Terminal apparatus, base station apparatus, and communication method

ABSTRACT

Uplink communication is efficiently performed in non-allocated frequencies. The terminal apparatus includes: a reception unit configured to receive downlink control information on a PDCCH; and a transmission unit configured to transmit a random access preamble. For a first frame structure type, the downlink control information is used to configure a subframe number of a first uplink subframe in which transmission of the random access preamble is allowed. For a second frame structure type, the downlink control information is used to configure a subframe number of a second uplink subframe in which transmission of the random access preamble is allowed and a symbol number of an uplink symbol in the second uplink subframe.

TECHNICAL FIELD

Embodiments of the present invention relate to a technique of a terminalapparatus, a base station apparatus, and a communication method thatenable efficient communication.

This application claims priority based on JP 2016-015283 filed in Japanon Jan. 29, 2016, the contents of which are incorporated herein byreference.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP), which is astandardization project, standardized the Evolved Universal TerrestrialRadio Access (hereinafter, referred to as E-UTRA), in which high-speedcommunication is realized by adopting an Orthogonal Frequency-DivisionMultiplexing (OFDM) communication scheme and flexible scheduling using aunit of prescribed frequency and time called resource block.

Moreover, the 3GPP discusses Advanced E-UTRA, which realizeshigher-speed data transmission and has upper compatibility with E-UTRA.E-UTRA relates to a communication system based on a network in whichbase station apparatuses have substantially the same cell configuration(cell size); however, regarding Advanced E-UTRA, discussion is made on acommunication system based on a network (different-type radio network,Heterogeneous Network) in which base station apparatuses (cells) havingdifferent configurations coexist in the same area. In this regard,E-UTRA is also referred to as “LTE (Long Term Evolution)”, and AdvancedE-UTRA is also referred to as “LTE-Advanced”. Furthermore, LTE may be acollective name including LTE-Advanced.

A Carrier Aggregation (CA) technique and a Dual Connectivity (DC)technique are specified, in which, in a communication system where cells(macro cells) having large cell radii and cells (small cells) havingsmaller cell radii than those of the macro cells coexist as in aheterogeneous network, a terminal apparatus performs communication byconnecting to a macro cell and a small cell simultaneously (NPL 1).

Meanwhile, NPL 2 studies Licensed-Assisted Access (LAA). According toLAA, a non-allocated frequency band (Unlicensed spectrum) used by awireless Local Area Network (LAN) is used as LTE. More specifically, thenon-allocated frequency band is configured as a secondary cell(secondary component carrier). Connection, communication, and/or aconfiguration of the secondary cell(s) used as LAA are assisted by aprimary cell (primary component carrier) configured to an allocatedfrequency band (Licensed spectrum). LAA widens a frequency band that isavailable for LTE, and thus wide band transmission is enabled. In thisregard, LAA is used in a shared frequency band (shared spectrum) sharedbetween prescribed operators.

In a case that a terminal apparatus transmits an uplink signal in anynon-allocated frequency, the terminal apparatus is not able to usedesired transmit power. This may reduce transmission quality.

CITATION LIST Non Patent Literature

NPL 1: 3rd Generation Partnership Project; Technical Specification GroupRadio Access Network; Evolved Universal Terrestrial Radio Access(E-UTRA); Physical layer procedures (Release 12), 3GPP TS 36.213 V12.4.0(2014-12).

NPL 2: 3rd Generation Partnership Project; Technical Specification GroupRadio Access Network; Study on Licensed-Assisted Access to UnlicensedSpectrum; (Release 13), 3GPP TR 36.889 V1.0.1 (2015-6).

SUMMARY OF INVENTION Technical Problem

However, for radio communication systems as that described above, noconcrete uplink communication method has been sufficiently studied.

The present invention has been made in light of the foregoing, and anobject of the present invention is to provide a terminal apparatus, abase station apparatus, and a communication method which enableefficient uplink communication.

Solution to Problem

(1) To accomplish the object described above, the present invention iscontrived to provide the following means. Specifically, a first aspectof the present invention is a terminal apparatus including: a receptionunit configured to receive downlink control information on a PDCCH; anda transmission unit configured to transmit a random access preamble. Fora first frame structure type, the downlink control information is usedto configure a subframe number of a first uplink subframe in whichtransmission of the random access preamble is allowed. For a secondframe structure type (the second frame structure type may be applied toan LAA secondary cell operation cell), the downlink control informationis used to configure a subframe number of a second uplink subframe inwhich transmission of the random access preamble is allowed and a symbolnumber of an uplink symbol in the second uplink subframe.

(2) A second aspect of the present embodiment is a base stationapparatus including: a transmission unit configured to transmit downlinkcontrol information on a PDCCH; and a reception unit configured toreceive a random access preamble. For a first frame structure type, thedownlink control information is used to configure a subframe number of afirst uplink subframe in which transmission of the random accesspreamble is allowed. For a second frame structure type (the second framestructure type may be applied to an LAA secondary cell operation cell),the downlink control information is used to configure a subframe numberof a second uplink subframe in which transmission of the random accesspreamble is allowed and a symbol number of an uplink symbol in thesecond uplink subframe.

(3) A third aspect of the present embodiment is a communication methodof a terminal apparatus, the communication method including the stepsof: receiving downlink control information on a PDCCH; and transmittinga random access preamble. For a first frame structure type, the downlinkcontrol information is used to configure a subframe number of a firstuplink subframe in which transmission of the random access preamble isallowed. For a second frame structure type, the downlink controlinformation is used to configure a subframe number of a second uplinksubframe in which transmission of the random access preamble is allowedand a symbol number of an uplink symbol in the second uplink subframe.

(4) A fourth aspect of the present embodiment is a communication methodof a base station apparatus, the communication method including thesteps of: transmitting downlink control information on a PDCCH; andreceiving a random access preamble. For a first frame structure type,the downlink control information is used to configure a subframe numberof a first uplink subframe in which transmission of the random accesspreamble is allowed. For a second frame structure type, the downlinkcontrol information is used to configure a subframe number of a seconduplink subframe in which transmission of the random access preamble isallowed and a symbol number of an uplink symbol in the second uplinksubframe.

Advantageous Effects of Invention

The present invention can provide improved transmission efficiency in aradio communication system in which a base station apparatus and aterminal apparatus communicate with each other.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example of a downlink radio frameconfiguration according to a present embodiment.

FIG. 2 is a diagram illustrating an example of an uplink radio frameconfiguration according to the present embodiment.

FIG. 3 is a schematic diagram illustrating an example of a blockconfiguration of a base station apparatus 2 according to the presentembodiment.

FIG. 4 is a schematic diagram illustrating an example of a blockconfiguration of a terminal apparatus 1 according to the presentembodiment.

FIG. 5 is a diagram illustrating an example of a downlink signalconfiguration according to the present embodiment.

FIG. 6 is a diagram illustrating an example of a procedure of CCA for adownlink transmission according to the present embodiment.

FIGS. 7A to 7C are diagrams illustrating an example of a relationshipbetween an interval, between a downlink transmission and an uplinktransmission, and types of CCA according to the present embodiment.

FIG. 8 is a diagram illustrating an example of a procedure of CCA for anuplink transmission according to the present embodiment.

FIG. 9 is a diagram illustrating an example of a procedure of CCA for anuplink transmission according to the present embodiment.

FIG. 10 is a diagram illustrating an example of frequency multiplexingof a physical uplink shared channel according to the present embodiment.

FIG. 11 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 12 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 13 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 14 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 15 is a diagram illustrating an example of a procedure of CCA foran uplink transmission according to the present embodiment.

FIG. 16 is a diagram illustrating an example of a PRACH configurationaccording to the present embodiment.

FIG. 17 is a diagram illustrating an example of the PRACH configurationaccording to the present embodiment.

FIG. 18 is a diagram illustrating an example a second PRACH preambletransmission method of the terminal apparatus according to the presentembodiment.

FIG. 19 is a table illustrating an example of correspondence betweenPRACH mask indices and PRACH resources according to the presentembodiment.

FIG. 20 is a diagram illustrating an example of a random access responseaccording to the present embodiment.

FIG. 21 is a diagram illustrating an example of reservation resourcesconfigured for the terminal apparatus according to the presentembodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

A first embodiment of the present invention will be described below. Adescription will be given by using a communication system (cellularsystem) in which a base station apparatus (base station, NodeB, oreNodeB (eNB)) and a terminal apparatus (terminal, mobile station, a userdevice, or User equipment (UE)) communicate in a cell.

A physical channel and a physical signal substantially used in EUTRA andAdvanced EUTRA will be described. The “channel” refers to a medium usedto transmit a signal, and the “physical channel” refers to a physicalmedium used to transmit a signal. In the present embodiment, thephysical channel may be used synonymously with “signal.” In the futureEUTRA and Advanced EUTRA, the physical channel may be added or itsconstitution and format type may be changed or added; however, thedescription of the present embodiment will not be affected even in acase where the channel is changed or added.

In LTE, EUTRA, and Advanced EUTRA, scheduling of a physical channel or aphysical signal is managed by using radio frames. One radio frame is 10ms in time length, and one radio frame includes 10 subframes. Inaddition, one subframe includes two slots. In other words, one subframeis 1 ms in time length, and one slot is 0.5 ms in time length. Moreover,scheduling is managed by using a resource block as a minimum unit ofscheduling for allocating a physical channel. The resource block isdefined by a given frequency domain including a set of multiplesubcarriers (e.g., 12 subcarriers having subcarrier spacings of 15 kHz)on a frequency axis and a domain including a given transmission timeintervals (TTIs, slots, symbols). Note that one subframe may be referredto as one resource block pair. In LTE, one TTI may basically be definedas one subframe (1 ms). The TTI may be defined as reception timeintervals on a reception side. TTI may be defined as a transmission unitor a reception unit of a physical channel, a physical signal, and thelike. In other words, the time lengths of a physical channel, a physicalsignal, and the like may be defined based on the length of the TTI.

In the EUTRA and Advanced EUTRA, a frame structure type is defined.Frame structure type 1 is applicable to Frequency Division Duplex (FDD).Frame structure type 2 is applicable to Time Division Duplex (TDD).

FIG. 1 is a diagram illustrating an example of a downlink radio frameconfiguration according to the present embodiment. In the downlink, anOFDM access scheme is used. Transmission of a downlink signal and/or ona downlink physical channel in the downlink is referred to as a downlinktransmission. In the downlink, a PDCCH, an EPDCCH, a Physical DownlinkShared CHannel (PDSCH), and the like are allocated. A downlink radioframe is constituted by a downlink Resource Block (RB) pair. Thisdownlink RB pair is a unit for allocation of a downlink radio resourceand the like and is based on the frequency band of a predefined width(RB bandwidth) and a time duration (two slots=1 subframe). Each of thedownlink RB pairs is constituted of two downlink RBs (RB bandwidth×slot)that are contiguous in time domain. Each of the downlink RBs isconstituted of 12 subcarriers in frequency domain. In the time domain,the downlink RB is constituted of seven OFDM symbols when a normalcyclic prefix (CP) is added, while the downlink RB is constituted of sixOFDM symbols when a cyclic prefix that is longer than the normal cyclicprefix is added. A region defined by a single subcarrier in thefrequency domain and a single OFDM symbol in the time domain is referredto as “Resource Element (RE)”. A physical downlink control channel is aphysical channel on which downlink control information such as aterminal apparatus identifier, physical downlink shared channelscheduling information, physical uplink shared channel schedulinginformation, and a modulation scheme, coding rate, and retransmissionparameter are transmitted. Note that although a downlink subframe in asingle Component Carrier (CC) is described here, a downlink subframe isdefined for each CC and downlink subframes are approximatelysynchronized between the CCs.

In the downlink, synchronization signals are assigned. Thesynchronization signals are used to adjust timings for downlink signalsand/or channels mainly between a base station apparatus transmittingdownlink signals and/or channels and a terminal apparatus receivingdownlink signals and/or channels. Specifically, at the terminalapparatus, synchronization signal is used to adjust timings of receivingradio frames or subframes, or OFDM symbols. At the terminal apparatus, asynchronization signal is also used to detect a center frequency of acomponent carrier. At the terminal apparatus, a synchronization signalis also used to detect the CP length of an OFDM symbol. At the terminalapparatus, a synchronization signal is also used to identify the cell(base station apparatus) from which the synchronization signal has beentransmitted. In other words, at the terminal apparatus, asynchronization signal is used to detect a cell identity of the cellfrom which the synchronization signal has been transmitted. Note that,at the terminal apparatus, a synchronization signal may be used toperform Automatic Gain Control (AGC). Note that, at the terminalapparatus, a synchronization signal may be used to adjust a timing ofprocessing symbol to be used for Fast Fourier Transform (FFT). Notethat, at the terminal apparatus, a synchronization signal may be used tocalculate Reference Signal Received Power (RSRP). Note that asynchronization signal may be used to secure a channel on which thesynchronization signal is to be transmitted.

A primary synchronization signal (first primary synchronization signal)and a secondary synchronization signal (first secondary synchronizationsignal) are transmitted on the downlink to promote cell searches. Cellsearch is a procedure performed by the terminal apparatus to acquiretime and frequency synchronization with the cell to detect a physicallayer Cell ID of the cell. E-UTRA cell search supports a flexible andgeneral transmission bandwidth corresponding to six or more resourceblocks.

A specific example of assignment (arrangement, mapping) of the primarysynchronization signal and the secondary synchronization signal will bedescribed. FIG. 9 illustrates mathematical expressions for determiningsubcarriers and OFDM symbols to which a synchronization signal ismapped. Assume that k is defined as a frequency domain, and l is definedas an index specifying a resource element in the time domain. A primarysynchronization signal and a secondary synchronization signal aredefined by Mathematical Expression (0−a), Mathematical Expression (1−a),and Mathematical Expression (2) in FIG. 9. Here, NR_(RB) ^(DL) denotesthe number of resource blocks specified based on configurationinformation about the downlink bandwidth, N_(SC) ^(RB) denotes afrequency domain uplink resource block size corresponding to the numberof subcarriers per resource block, and N_(symbol) ^(DL) denotes thenumber of OFDM symbols per downlink slot. Here, a_(k, 1) denotes asymbol in a resource element (k, l), d denotes a sequence, and n takes avalue from 0 to 2N_(M)−1. Moreover, mod denotes a function representinga remainder, and A mod B denotes a remainder in a case that A is dividedby B. Here, for the primary synchronization signal and the secondarysynchronization signal, N_(M) is 31. Here, for the primarysynchronization signal and the secondary synchronization signal, h is 1.

The Primary Synchronization Signal (PSS) and the SecondarySynchronization Signal (SSS) illustrated in FIG. 1 are transmitted using62 subcarriers (62 resource elements) around a center frequencyregardless of the downlink bandwidth (a system bandwidth of thedownlink, a downlink transmission bandwidth). A direct-currentsubcarrier (DC subcarrier) corresponding to the center of thesubcarriers within the system bandwidth is not used as the primarysynchronization signal or the secondary synchronization signal. Fivesubcarriers (five resource elements) at each of opposite ends of each ofthe primary synchronization signal and the secondary synchronizationsignal are reserved and not used for transmission of the primarysynchronization signal or the secondary synchronization signal. Theresource elements including the five resource elements at each end inaddition to the above-described 62 resource elements are referred to asthe primary synchronization signal and the secondary synchronizationsignal.

Although not illustrated here, a physical broadcast information channelmay be allocated and a downlink Reference Signal (RS) may be assigned,to a downlink subframe. Examples of a downlink reference signal are aCell-specific RS (CRS), which is transmitted through the sametransmission port as that for a PDCCH, a Channel State Information RS(CSI-RS, non-zero power CSI-RS, NZP CSI-RS), which is used to measureChannel State Information (CSI), a terminal-specific RS (UE-specific RS(URS)), which is transmitted through the same transmission port as thatfor one or some PDSCHs, and a Demodulation RS (DMRS), which istransmitted through the same transmission port as that for an EPDCCH.Moreover, carriers on which no CRS is mapped may be used. In this case,a similar signal (referred to as “enhanced synchronization signal”) to asignal corresponding to one or some transmission ports (e.g., onlytransmission port 0) or all the transmission ports for the CRSs can beinserted into one or some subframes (e.g., the first and sixth subframesin the radio frame) as time and/or frequency tracking signals. Theterminal-specific reference signals transmitted at the same transmissionport as part of PDSCHs are also referred to as terminal-specificreference signals or DMRSs associated with PDSCHs. The demodulationreference signals transmitted at the same transmission port as theEPDCCHs are also referred to as DMRSs associated with the EPDCCHs.

Although not illustrated here, in the downlink subframe, Zero PowerCSI-RS (ZP CSI-RS) mostly used for rate matching of the PDSCH, which istransmitted simultaneously with the downlink subframe, and CSIInterference Management (CSI-IM) mostly used for interferencemeasurement of channel state information may be mapped. The zero powerCSI-RS and the CSI-IM may be arranged on resource elements where thenon-zero power CSI-RS can be mapped. The CSI-IM may be configured tooverlap the non-zero CSI-RS.

Although not illustrated, Discovery Signals (DSs) may be arranged indownlink subframes. In a certain cell, a DS (DS Occasion) is constitutedof a time period. (DS period) of a prescribed number of contiguoussubframes. The prescribed number is one to five according to FDD (Framestructure type 1) and two to five according to TDD (Frame structure type2). The prescribed number is configured by the RRC signaling. Theterminal apparatus is configured to have an occasion when the DS periodis measured. The configuration of the occasion when the DS period ismeasured is also referred to as a Discovery signals measurement tintingconfiguration (DMTC). The occasion (DMTC Occasion) when the terminalapparatus measures the DS period is configured by an occasioncorresponding to 6 ms (six subframes). The terminal assumes that the DSis transmitted (is mapped or occurs) per subframe configured by aparameter dmtc-Periodicity configured by the RRC signaling. The terminalassumes a presence of the DS configured to include following signals indownlink subframes.

(1) A CRS of antenna port 0 in a DwPTS of all downlink subframes and allspecial subframes in the DS period.

(2) A PSS in a first subframe of the DS period according to FDD. A PSSin the second subframe of the DS period according to TDD.

(3) A SSS in the first subframe of the DS period.

(4) A non-zero power CSI-RS in a zero or more subframes of the DSperiod. This non-zero power CSI-RS is configured by the RRC signaling.

The terminal performs measurements based on the configured DS. Themeasurements are performed by using the CRS of the DS or the non-zeropower CSI-RS of the DS. The configuration related to the DS canconfigure multiple non-zero power CSI-RSs.

FIG. 2 is a diagram illustrating an example of an uplink radio frameconfiguration according to the present embodiment. An SC-FDMA scheme isused in the uplink. Transmission of an uplink signal and/or on an uplinkphysical channel in the uplink is referred to as an uplink transmission.That is, the uplink transmission can be rephrased as transmission of aPUSCH. In the uplink, a Physical Uplink Shared Channel (PUSCH), a PUCCH,and the like are allocated. An uplink reference signal is assigned toone or some of PUSCHs and PUCCHs. An uplink radio frame is constitutedof uplink RB pairs. This uplink RB pair is a unit for allocation ofuplink radio resources and the like and is constituted by the frequencyband of a predefined width (RB bandwidth) and a predetermined timeduration (two slots=1 subframe). Each of the uplink RB pairs isconstituted of two uplink RBs (RB bandwidth×slot) that are contiguous inthe time domain. Each of the uplink RB is constituted of 12 subcarriersin the frequency domain. In the time domain, the uplink RB isconstituted of seven SC-FDMA symbols in a case that a normal cyclicprefix is added, while the uplink RB is constituted of six SC-FDMAsymbols in a case that a cyclic prefix that is longer than the normalcyclic prefix is added. Note that although an uplink subframe in asingle CC is described here, an uplink subframe is defined for each CC.For compensation of propagation delay and the like, the beginning of theradio frame in the uplink (uplink subframe) is adjusted to precede thebeginning of the radio frame in the downlink (downlink subframe), withrespect to the terminal apparatus.

A synchronization signal is constituted by three kinds of primarysynchronization signals and secondary synchronization signalsconstituted by 31 kinds of codes that are interleaved in the frequencyregion. 504 patterns of cell identifiers (Physical Cell Identities;PCIs) for identifying base station apparatuses, and frame timing forradio synchronization are indicated by the combinations of the primarysynchronization signals and the secondary synchronization signals. Theterminal apparatus identifies the physical cell ID of a receivedsynchronization signal by cell search.

The Physical Broadcast Channel (PBCH) is transmitted for thenotification (configuration) of a control parameter (broadcastinformation i.e., System information) commonly used among the terminalapparatuses within the cell. The radio resource in which broadcastinformation is transmitted is announced on the physical downlink controlchannel to the terminal apparatuses in the cell. Broadcast informationnot announced on the physical broadcast information channel istransmitted, as a layer-3 message (system information) for announcingthe broadcast information of the physical downlink shared channel, bythe announced radio resource.

Broadcast information to be notified includes, for example, a CellGlobal Identifier (CGI), which indicates a cell-specific identifier, aTracking Area Identifier (TAI) for managing standby areas in paging,random access configuration information (such as a transmission timingtimer), and shared radio resource configuration information, neighboringcell information and uplink access control information of the cell.

A downlink reference signal is classified into multiple types accordingto its use. For example, cell-specific RSs (Cell-specific referencesignals) are pilot signals transmitted with prescribed power from eachcell and are downlink reference signals periodically repeated in thefrequency domain and the time domain under a prescribed rule. Theterminal apparatus receives the cell-specific RS and thus measures thereception quality of each cell. The terminal apparatus also uses acell-specific RS as a reference signal for demodulation of a physicaldownlink control channel or a physical downlink shared channeltransmitted at the same time as a cell-specific RS. A sequencedistinguishable among the cells can be used for a sequence for acell-specific RS.

The downlink reference signal is also used for estimation of downlinkchannel fluctuation. A downlink reference signal used for estimation ofdownlink channel fluctuations is referred to as “Channel StateInformation Reference Signal (CSI-RS)”. A downlink reference signalindividually configured for the terminal apparatus is referred to as UEspecific Reference Signal (URS), a Demodulation Reference Signal (DMRS),or a Dedicated RS (DRS), and is referred to for a channel compensationprocess for demodulating an enhanced physical downlink control channelor a physical downlink shared channel.

The Physical Downlink Control Channel (PDCCH) occupying one or severalOFDM symbols (e.g., 1 to 4 OFDM symbols) from the start of each subframeis transmitted. The Enhanced Physical Downlink Control Channel (EPDCCH)is a physical downlink control channel allocated to the OFDM symbols towhich the Physical Downlink Shared CHannel (PDSCH) is allocated. ThePDCCH or EPDCCH is used for notifying each terminal apparatus of radioresource allocation information according to scheduling determined bythe base station apparatus and information indicating an adjustmentamount for an increase or decrease in transmit power. In the following,even in a case that the Physical Downlink Control Channel (PDCCH) aloneis described, both physical channels that is, the PDCCH and the EPDCCH,are included unless otherwise noted.

The terminal apparatus needs to monitor a physical downlink controlchannel addressed to the terminal apparatus itself, and receive thephysical downlink control channel addressed to the terminal apparatusitself, before transmitting and/or receiving downlink data or a layer-2message or layer-3 message, which is higher-layer control information(such as a paging or handover command), and thus acquire, from thephysical downlink control channel, radio resource allocation informationcalled uplink grant in a case of transmission and downlink grant(downlink assignment) in a case of reception. Note that it is alsopossible to constitute the physical downlink control channel so that thephysical downlink control channel is to be transmitted in the dedicatedresource block domain allocated to each terminal apparatus by the basestation apparatus, instead of transmission through OFDM symbolsdescribed above. The uplink grant can be rephrased as a DCI format usedfor scheduling the PUSCH. The downlink grant can be rephrased as a DCIformat used for scheduling the PDSCH. The subframe for which the PDSCHis scheduled is a subframe for which the DCI format indicating receptionof the PDSCH, has been successfully decoded. The subframe for which thePUSCH is scheduled is indicated in association with the subframe forwhich the DCI format indicating transmission of the PUSCH has beensuccessfully decoded. For example, for FDD cells, the subframe for whichthe PUSCH is scheduled is the fourth subframe following the subframe forwhich the DCI format indicating transmission of the PUSCH has beensuccessfully decoded. In other words, each of the subframes for whichthe PUSCH and the PDSCH are scheduled is associated with the subframefor which the DCI format indicating the transmission or reception of thechannel has been successfully decoded.

The Physical Uplink Control Channel (PUCCH) is used for anacknowledgment in response to reception of downlink data transmitted onthe physical downlink shared channel (HARQ-ACK; Hybrid Automatic RepeatreQuest-Acknowledgment or ACK/NACK; Acknowledgment/NegativeAcknowledgment), downlink channel (Channel State) information (CSI), anduplink radio resource allocation request (radio resource request,Scheduling Request (SR)).

CSI includes a Channel Quality Indicator (CQI) of the serving cellcorresponding to the CSI, a Precoding Matrix indicator (PMI), aPrecoding Type Indicator (PTI), and a Rank Indicator (RI), which can beused respectively for specifying (representing) a preferable modulationscheme and coding rate, a preferable precoding matrix, a preferable PMItype, and a preferable rank. Indication may be used as a notation foreach Indicator. Moreover, the CQI and the PMI are classified intowideband CQI and PMI assuming transmission using all the resource blocksin a single cell, and subband CQI and PMI assuming transmission usingsome contiguous resource blocks (subbands) in a single cell. Moreover,PMI may include a type of PMI, which represents a single preferableprecoding matrix using two types of PMIs, which are a first PMI and asecond PMI, in addition to a normal type of PMI, which represents asingle preferable precoding matrix using a single PMI.

For example, the terminal apparatus 1 reports a CQI index that satisfiesa condition that an error probability of one PDSCH transport occupying agroup of downlink physical resource blocks and determined by acombination of a modulation scheme and a transport block sizecorresponding to the CQI index, does not exceed a prescribed value (forexample, 0.1).

Note that each of the downlink physical resource blocks used tocalculate the CQI, the PMI, and/or the RI is referred to as a CSIreference resource.

The terminal apparatus 1 reports the CSI to the base station apparatus2. The CSI reporting includes periodic CSI reporting and aperiodic CSIreporting. In the periodic CSI reporting, the terminal apparatus 1reports the CSI at a timing configured by a higher layer. In theaperiodic CSI reporting, the terminal apparatus 1 reports the CSI at atiming based on CSI request information included in the received uplinkDCI format (uplink grant) or a random access response grant.

The terminal apparatus 1 reports the CQI and/or the PMI and/or the RI.Note that the terminal apparatus 1 need not report the PMI and/or the RIdepending on a configuration made by a higher layer. The configurationmade by the higher layer includes, for example, a transmission mode, afeedback mode, a reporting type, and a parameter indicating whether toreport the PMI/RI.

Moreover, the terminal apparatus 1 may be configured to perform one ormultiple CSI processes for one serving cell. The CSI process isconfigured in association with the CSI reporting. One CSI process isassociated with one CSI-RS resource and one CSI-IM resource.

The Physical Downlink Shared Channel (PDSCH) is also used to notify theterminal apparatus of a response to random access (Random AccessResponse (RAR)) and broadcast information (system information) that isnot notified by paging or on the physical broadcast information channel,in addition to downlink data, as a layer-3 message. Radio resourceallocation information of the physical downlink shared channel isindicated by a physical downlink control channel. The physical downlinkshared channel is allocated to OFDM symbols other than the OFDM symbolsused to transmit a physical downlink control channel and is transmitted.In other words, the physical downlink shared channel and the physicaldownlink control channel are time division multiplexed in a singlesubframe.

The Physical Uplink Shared Channel (PUSCH) mainly transmits uplink dataand uplink control information which may also include uplink controlinformation such as CSI and ACK/NACK. Moreover, the physical uplinkshared channel is also used such that the terminal apparatus notifiesthe base station apparatus of uplink data as well as a layer-2 messageand a layer-3 message, which are higher-layer control information. Radioresource allocation information of the physical uplink shared channel isprovided by a physical downlink control channel, as in a case ofdownlink.

An Uplink Reference Signal (also referred to as “uplink pilot signal” or“uplink pilot channel”) includes a Demodulation Reference Signal (DMRS)to be used by the base station apparatus to demodulate the PhysicalUplink Control Channel PUCCH and/or Physical Uplink Shared ChannelPUSCH, and a Sounding Reference Signal (SRS) to be mainly used by thebase station apparatus to estimate an uplink channel state. Moreover,sounding reference signals are categorized into a periodic SoundingReference Signal (Periodic SRS), which is transmitted periodically, oran Aperiodic Sounding Reference Signal (Aperiodic SRS), which istransmitted in a case that transmission is instructed by the basestation apparatus.

A Physical Random Access Channel (PRACH) is a channel used for thenotification (configuration) of a preamble sequence and includes a guardtime. The preamble sequence is configured such that multiple sequencesare used for notifying information to the base station apparatus. Forexample, in a case that 64 sequences are available, 6-bit informationcan be provided to the base station apparatus. A physical random accesschannel is used by the terminal apparatus as a means for accessing thebase station apparatus.

The PRACH is used to transmit a random access preamble (PRACH preamble).The PRACH is used for the initial connection establishment procedure,the handover procedure, the connection re-establishment procedure,synchronization (timing adjustment) for uplink transmission, and therequest for the PUSCH resource.

FIG. 16 is a diagram illustrating an example of a configuration of aPRACH (or a PRACH preamble) (also referred to as a first PRACH or afirst PRACH preamble, below) according to the present embodiment. Thefirst PRACH is mapped to a frequency band corresponding to six RBs (1.08MHz) and includes 839 subcarriers (subcarrier spacings of 1250 Hz)(region indicated by oblique lines in FIG. 16). The PRACH preamble(random access preamble sequence) transmitted on the first PRACH is 839in length. 13 subcarriers and 12 subcarriers that are outermost in thefrequency direction of the first PRACH are not used (also referred to asGuard bands or Guard carriers). A Cyclic Prefix (CP) is mapped to thebeginning of the first PRACH in the time direction, and an end portionis a region that is not used (also referred to as Guard Time or thelike). Note that the configuration of the first PRACH defined in LTE isnot limited to that illustrated in FIG. 16. For the configuration of thefirst PRACH, a parameter (also referred to as a first parameter below)is determined based on a Preamble format (random access preamble format)notified through higher layer signalling. The first PRACH may be mappedto the frequency band, corresponding to six RBs (1.08 MHz) and includes139 subcarriers (subcarrier spacings of 7500 Hz).

FIG. 17 is a diagram illustrating another example of the configurationof the PRACH (also referred to as a second PRACH, a second PRACHpreamble, or PRACH preamble format 5, below) according to the presentembodiment. The second PRACH is mapped to a wider band than that for thefirst PRACH. The example illustrated in FIG. 17 is a configuration inwhich the second PRACH and Guard carriers are mapped to the entire ULband. Note that Guard carriers do not need to be mapped, and the secondPRACH may include 839 subcarriers or 139 subcarriers, or the number ofsubcarriers different from 839 and 139. The PRACH preamble (randomaccess preamble sequence) transmitted on the second PRACH may be 839 or139 in length or may have a length different from 839 or 139. Further, achannel (PUSCH, PUCCH, first PRACH, second PRACH, and the like) otherthan the second PRACH may be mapped to outer sides of the Guard carriersinstead of the second PRACH and Guard carriers being mapped to theentire U band. The second PRACH and the Guard carriers may be mapped topart of the entire UL band. The PRACH and the Guard carriers may bemapped to a band wider than 1.08 MHz (six RBs). In other words, theproduct of the subcarrier spacing of the second PRACH and the length ofthe PRACH preamble transmitted on the second PRACH may be greater than1.08 MHz. Using the band wider than 1.08 MHz (six RBs) (e.g., the entireUL band) increases the subcarrier spacings of the second PRACH and hencereduces the time to be used for the PRACH.

As described above, the PRACH (which may be a PRACH preamble or a randomaccess preamble) may include a CP and a sequence part (preamble sequencepart). Specifically, a different CP length and/or a different sequencelength may be defined for each one or multiple Preamble formats (e.g.,Preamble formats 0, 1, 3, and/or 4) used as the first PRACH. A differentCP length and/or a different sequence length may be used for each one ormultiple Preamble formats (e.g., Preamble formats 5 and/or 6) used asthe second PRACH.

Here, the parameter (first parameter) associated with the Preambleformat may include the CP length used to define the Preamble format. Thefirst parameter may include the sequence length used to define thePreamble format. In other words, the first parameter may include aparameter (parameter associated with the PRACH) used to define thePreamble format.

Here, as will be described below, the first parameter may be used basedon a frame structure type (e.g., a first frame structure type (FS1), asecond frame structure type (FS2), and/or a third frame structure type(FS3)).

For example, Preamble formats 0, 1, 2, and/or 3 may be used for thefirst frame structure type (FS1). Preamble formats 0, 1, 2, 3, and/or 4may be used for the second frame structure type (FS2). Preamble formats0, 1, 2, 3, 4, 5, and/or 6 may be used for the third frame structuretype (FS3). Here, only Preamble formats 5 and/or 6 only second PRACH)may be used for the third frame structure type (FS3).

A time resource to which the PRACH is mapped is determined based atleast on information (PRACH-config) notified through higher layersignalling. The terminal apparatus determines mapping (time resource) ofthe PRACH, based on the information notified through the higher layersignalling and transmits the PRACH preamble using the determined mapping(time resource) of the PRACH.

FIG. 18 is a diagram illustrating an example of a method in which theterminal apparatus transmits the second PRACH preamble. Each of theterminal apparatuses 1-A, B, and C transmits a PRACH preamble by using aPRACH resource determined based on information notified through thehigher layer signalling. For example, in a case that the terminalapparatus 1-A transmits the first PRACH preamble, the PRACH resource isoccupied by the PRACH preamble transmitted by the terminal apparatus1-A. Meanwhile, in a case that the terminal apparatus 1-B transmits thesecond PRACH preamble, part of the PRACH resource remains, and hence theterminal apparatus 1-C is able to transmit the second PRACH preamble inthe same PRACH resource without affecting the second PRACH preambletransmitted by the terminal apparatus 1-A.

The second PRACH preamble transmitted by the terminal apparatus 1 (theterminal apparatus 1 includes the terminal apparatuses 1-A, B, and C) isshorter than the period of the PRACH resource determined through higherlayer signalling. Hence, multiple terminal apparatuses 1 can transmitthe second PRACH preamble at different timings by using one PRACHresource. In other words, one PRACH resource is divided into multiplesub-resources (sub-sections, PRACH slots, transmission time points,transmission timings, or the like), and the terminal apparatuses 1 cantransmit the second PRACH preamble in the respective PRACH slots.

Note that the configuration of the PRACH resources and PRACH slots isnot limited to the above. For example, the PRACH resource may correspondto one OFDM symbol or one SC-FDMA symbol length or may correspond to thesubframe length or slot length.

The terminal apparatus according to the present embodiment can use thefirst PRACH preamble or the second PRACH preamble (is configured withfirst PRACH preamble transmission or second PRACH preambletransmission), based on higher layer signalling and/or cellidentification information, and/or other signalling from the eNB, and/orthe like. For example, the higher layer signalling includes informationincluded in a MIB, information included in a SIB, information specifyinga PRACH resource (e.g., PRACH-config, PRACH Configuration Index), andthe like. For example, other signalling by the eNB includes informationincluded in the PDCCH (e.g., information included in a PDCCH order orthe like). The higher layer signalling and/or cell identificationinformation, and/or other signalling from the eNB, and/or the like isalso referred to as a second parameter below.

Note that for the PDCCH order, the Localized/Distributed VirtualResource Block (VRB) assignment flag field is configured at 0. The PDCCHorder, the Resource block assignment field is all configured at 0. ThePDCCH order includes information (Preamble index) specifying the PRACHpreamble index to be used by the terminal apparatus. In a case that thePreamble Index included in the PDCCH order is 000000, the terminalapparatus transmits a PRACH preamble by using the PRACH preamble indexdetermined by the terminal apparatus.

The terminal apparatus 1 refers to a table (e.g., a table relating torandom access configuration) to acquire information on a PRACH resourceand the like. The terminal apparatus 1 may determine a table to refer toin order to acquire the information on a PRACH resource and the like,based on whether the first PRACH preamble transmission is configured orthe second PRACH preamble transmission is configured. The table (alsoreferred to as a first table below) to be referred to by the terminalapparatus 1 to acquire information on a PRACH resource and the like,based on the PRACH Configuration Index, in a case that the first PRACHpreamble transmission is configured and the table (also referred to as asecond table below) to be referred to by the terminal apparatus 1 in acase that the second PRACH preamble transmission is configured may bedifferent from each other. In other words, the terminal apparatus 1 mayuse different methods of determining a PRACH resource in a case that thefirst PRACH preamble transmission is configured and a case that thesecond PRACH preamble transmission is configured. In the case that thefirst PRACH preamble transmission is configured, the terminal apparatus1 refers to the PRACH Configuration index to acquire information on aPRACH resource and the like. In the case that the second PRACH preambletransmission is configured, the terminal apparatus 1 does not need torefer to the PRACH Configuration Index to acquire information on a PRACHresource and the like.

For example, the terminal apparatus may refer to the first table, basedon the PRACH Configuration Index, in frame structure type 1 whilereferring to the second table, based on the PRACH Configuration Index,in frame structure type 3.

In other words, for PRACH (which may be PRACH preamble or random accesspreamble) transmission, time resource and/or frequency resource islimited. Here, the above-described PRACH resource may include timeresource and/or a frequency resource for the PRACH transmission. Here,the time resource to be used for the PRACH transmission may be indicatedby using a subframe number in the radio frame. The time resource to beused for the PRACH transmission may be indicated by using a PRACH slot.The frequency resource to be used for the PRACH transmission may beindicated by using a physical resource block (index of the physicalresource block).

Here, the PRACH slot may be synonymous with symbols (slot) in thesubframe. In other words, the PRACH slot number may be synonymous withthe numbers corresponding to the symbols (slot number) in the subframe.The PRACH slot number may be synonymous with the number of the symbol(number of the slot) at which the PRACH transmission is started in thesubframe. The frequency resource to be used for the PRACH transmissionmay be indicated by using a physical resource block (index of thephysical resource block).

The base station apparatus may indicate a random access configuration bytransmitting the second parameter. Here, the random access configurationmay include a PRACH resource. Moreover, the random access configurationmay include a preamble format, a system frame number, a subframe number,a PRACH slot number, and/or a frequency offset (frequency offset for aphysical resource block). For example, the base station apparatus mayconfigure a preamble format, a system frame number, a subframe number, aPRACH slot number, and/or a frequency offset (frequency offset for aphysical resource block) by transmitting the second parameter.

Here, the base station apparatus may transmit at least the secondparameter to configure (indicate) the subframe number to be used forPRACH transmission. As described above, for example, the secondparameter may include PRACH-config and/or PRACH Configuration Index.

Moreover, the base station apparatus may transmit at least the thirdparameter to configure (indicate) the PRACH slot number to be used forPRACH transmission. For example, the third parameter may includePRACH-config_r14 and/or PRACH Configuration Index 14.

In other words, the parameter (second parameter) for configuring thesubframe number to be used for PRACH transmission and the parameter(third parameter) for configuring the PRACH slot number to be used forPRACH transmission may be defined individually. Here, the slot numberconfigured by using the third parameter may be configured as a certainPRACH slot number in a certain subframe (e.g., PRACH slot number 1 insubframe number 3). Here, the certain subframe indicates a subframe in acertain radio frame.

The configuration based on the second parameter and/or the configurationbased on the third parameter may be used based on the frame structuretype (e.g., the first frame structure type (FS1), the second framestructure type (FS2), and/or the third frame structure type (FS3)).

For example, the configuration based on the second parameter may be usedfor the first frame structure type (FS1). Moreover, the configurationbased on the second parameter nay be used for the second frame structuretype (FS2). Moreover, the configuration based on the second parameterand/or the configuration based on the third parameter may be used forthe third frame structure type (FS3).

As described above, the terminal apparatus 1 may determine the randomaccess configuration in accordance with a configuration made by the basestation apparatus. For example, the terminal apparatus 1 for which thefirst PRACH preamble transmission is configured may adjust the start ofthe PRACH transmission to the start of the corresponding uplink subframe(configured uplink subframe). In other words, in a case that the firstPRACH preamble transmission is configured, the start of the PRACH may beadjusted to the start of the corresponding uplink subframe.

The terminal apparatus 1 for which the second PRACH preambletransmission is configured may adjust the start of the PRACHtransmission to the start of the corresponding uplink slot (configureduplink slot, PRACH slot number). In other words, the start of the PRACHmay be adjusted to the start of the corresponding uplink slot.Specifically, in a case that the second PRACH preamble transmission isconfigured, the start of the PRACH may be adjusted to the start of thecorresponding uplink slot.

Moreover, as described above, the terminal apparatus 1 may determine(acquire) the random access configuration (including information on aPRACH resource and the like) by referring to the first table and thesecond table. Here, the terminal apparatus 1 for which the second PRACHpreamble transmission is configured may determine (acquire) the randomaccess configuration (including information on a PRACH resource and thelike) by switching interpretation of the first table. For example, theterminal apparatus 1 for which the second PRACH preamble transmission isconfigured may determine the PRACH slot number (uplink slot) to be usedfor the PRACH transmission by switching interpretation of the firsttable. Here, the terminal apparatus 1 for which the first PRACH preambletransmission is configured may determine the subframe number (uplinksubframe) to be used for the PRACH transmission, based on the firsttable.

In other words, the terminal apparatus 1 may determine a differentconfiguration for the PRACH transmission by changing interpretation of asingle table, based on whether the first PRACH preamble transmission isconfigured or the second PRACH preamble transmission is configured. Forexample, the terminal apparatus 1 may interpret (presume) the value(parameter) set in a single table as a subframe at which the PRACHtransmission is started or a PRACH slot at which the PRACH transmissionis started.

In a case of a non-contention based random access procedure, the basestation apparatus can request the terminal apparatus to perform PRACHpreamble transmission. The frame (information) for requesting PRACHpreamble transmission can include a PRACH Preamble Index or/and a PRACHMask Index (e.g., the PDCCH order based on DCI format 1A).

In a case that the base station apparatus has requested PRACH preambletransmission, the terminal apparatus determines a configuration of thePRACH preamble and a PRACH resource to be used, based on the notifiedinformation (inform requesting PRACH preamble transmission).

FIG. 19 is a table illustrating example of correspondence between PRACHmask indices and PRACH resources. The terminal apparatus can determine aPRACH resource in which the second PRACH preamble is transmitted, basedon a PRACH Mask Index. The PRACH Mask Index corresponds to a PRACHResource Index, and the number assigned to each PRACH Resource Indexindicates information associated with the PRACH resource to be used bythe terminal apparatus. For example, in FDD, PRACH Resource Index 0corresponds to the PRACH resource indicated, based on the number ofPRACHs configured in one radio frame, by a number associated with eachof the PRACHs. For example, in the case of TDD, PRACH Resource Index 0corresponds to the PRACH resource indicated by a number associated witheach of the configured PRACHs sequentially in the frequency direction.

The base station apparatus can indicate the PRACH slot to be used by theterminal apparatus, using a PRACH Mask Index. The terminal apparatus canconfigure a subframe, a slot, a PRACH slot, and the like in which thePRACH preamble is transmitted, based on a PRACH Mask Index. The PRACHResource Index may correspond to a slot number, a PRACH slot number,or/and an OFDM symbol number, or the like.

The terminal apparatus can configure a PRACH resource, based on thecorrespondence in the table illustrated in FIG. 19 with the PRACH MaskIndex received in a case of transmitting the first PRACH and configure aPRACH resource, a slot number, a PRACH slot number or/and an OFDM symbolnumber by a method other than that using the correspondence based on thetable illustrated in FIG. 19 with the PRACH Mask Index received in acase of transmitting the second PRACH preamble. In other words, theterminal apparatus uses a different method of interpreting a PRACH MaskIndex differently or/and selecting a PRACH resource, depending on thePRACH preamble configuration.

The terminal apparatus uses the physical random access channel torequest an uplink radio resource in a case that no physical uplinkcontrol channel is configured for an SR or to request the base stationapparatus for a transmission timing adjustment information (alsoreferred to as Timing Advance (TA) command) necessary for matchinguplink transmission timing to a reception timing window of the basestation apparatus, for example. Moreover, the base station apparatus canrequest the terminal apparatus to start a random access procedure, byusing a physical downlink control channel.

The random access response is response information from the base stationapparatus for random access by the terminal apparatus. The random accessresponse is included in the PDSCH scheduled based on control informationfor the PDCCH having CRC scrambled with a Random Access-Radio NetworkTemporary Identifier (RA-RNTI), and the PDSCH is transmitted from thebase station apparatus. The random access response includes transmissiontiming adjustment information, the uplink grant (the uplink grantincluded in the random access response is also referred to as a randomaccess response grant), and Temporary C-RNTI information, which is atemporary identifier of the terminal apparatus.

Operations relating to a method of acquiring a random access response bythe terminal apparatus will be described. In a case that the terminalapparatus transmits the first PRACH preamble, the base station apparatustransmits a random access response to the terminal apparatus. Theterminal apparatus monitors the PDCCH or/and EPDCCH (both can bereferred to also as PDCCH below unless otherwise stated) transmittedfrom the base station apparatus in a case of transmitting the firstPRACH preamble. A value of the RA-RNTI to be used by the terminalapparatus to monitor the PDCCH is calculated in accordance with acalculation expression represented by 1+t_d+10*f_id. Note that t_ddenotes a value of the first subframe number (or index, the index of thefirst subframe, or the like) in the time resource to be used for thefirst PRACH preamble transmitted from the terminal apparatus. Moreover,f_id denotes a value based on the frequency resource to be used for thefirst MACH preamble transmitted from the terminal apparatus. Note thatt_id can take a value from 0 to 9, and f_id can take a value from 0 to 5(in a case of TDD). In the present embodiment, the RA-RNTI in a casethat the first PRACH preamble is transmitted from the terminal apparatusis also referred to as a first RA-RNTI, and the calculation expressionfor the first RA-RNTI is also referred to as a first calculationexpression.

In other words, the first calculation expression may be used tocalculate a RA-RNTI associated with the PRACH in which the first PRACHpreamble is transmitted. Here, in the first calculation expression, thesubframe (first subframe number) at which transmission of the firstPRACH preamble is started may be used.

Next, a random access response procedure in a case that the terminalapparatus transmits the second PRACH preamble will be described. In acase that the terminal apparatus transmits the second PRACH preamble,the base station apparatus can trans it a random access response to theterminal apparatus. The resource to be used for the random accessresponse to be transmitted from the base station apparatus to theterminal apparatus can be indicated by using the PDCCH.

For example, the base station apparatus may scramble the PDCCH, based onthe RA-RNTI relating to the first PRACH preamble. Specifically, CRCparity bits scrambled with the first RA-RNTI may be attached to downlinkcontrol information to be used for scheduling of the PDSCH in which therandom access response is transmitted. Here, the downlink controlinformation to which CRC parity bits scrambled with the first RA-RNTI istransmitted on the PDCCH.

Alternatively, the base station apparatus may scramble the PDCCH, basedon an RNTI (e.g., C-RNTI, SPS-RNTI, Temporary C-RNTI, or the like) otherthan the RA-RNTI. The base station apparatus can also scramble thePDCCH, based on the RA-RNTI calculated in accordance with a newcalculation expression. In the present embodiment, the RA-RNTI in a casethat the second PRACH preamble is transmitted from the terminalapparatus is also referred to as a second RA-RNTI, and the calculationexpression for the second RA-RNTI is also referred to as a secondcalculation expression.

Specifically, CRC parity bits attached to the downlink controlinformation to be used for scheduling of the PDSCH in which the randomaccess response is transmitted may be scrambled with the RA-RNTIcalculated by using the second calculation expression. In other words,the second calculation expression may be used to calculate a RA-RNTIassociated with the PRACH in which the second PRACH preamble istransmitted.

For example, in the second calculation expression, a PRACH slot number(Index, number, or the like) may be used. For example, in the secondcalculation expression, the PRACH slot (first PRACH slot number) atwhich transmission of the second PRACH preamble is started may be used.Moreover, according to the second calculation expression, calculationcan be performed based at least on the PRACH slot number and otherinformation.

For example, the second calculation expression can be represented asRA-RNTI=1+t_id+10*f_id+slot_id (PRACH slot number)+61*ceil(slot_id/N_id). Here, t_id may be a value based on the first PRACH slotnumber (or index, the index of the first slot, or the like) in the timeresource to be used for the second PRACH preamble transmitted from theterminal apparatus. Moreover, f_id may denote a value based on thefrequency resource to be used for the second PRACH preamble transmittedfrom the terminal apparatus. Here, ceil (*) denotes the smallest integergreater than *, and N_id denotes the total number of PRACH slots. Notethat the second calculation expression is not limited to the above.

The second calculation expression may be determined based on the symbollength of the second PRACH preamble. For example, as t_id in the secondcalculation expression, the length of the PRACH slot (length of thesymbols) used for the transmission of the second. PRACH preamble may beused.

The terminal apparatus performs a descrambling process on the PDCCH,based on the RA-RNTI (or another RNTI) to detect DCI (or a DCI format)from the PDCCH in which no error is detected (CRC match). Informationindicating a resource to be used for the PDSCH including the randomaccess response is contained in the PDCCH detected by the terminalapparatus, and the terminal apparatus can receive the PDSCH destined forthe terminal apparatus itself.

The random access response includes an uplink grant field to which anuplink grant is mapped and a Temporary C-RNTI field to which informationfor indicating a Temporary C-RNTI is mapped. The uplink grant includedin the random access response is also referred to as a random accessresponse grant.

FIG. 20 is a diagram illustrating an example of the random accessresponse according to the present embodiment.

In the downlink, one MAC Protocol Data Unit (PDU) is allowed to includemultiple random access responses. In FIG. 20, the MAC Random AccessResponse (RAR) indicates a random access response. The MAC PDU in FIG.20 includes one MAC header, n random access responses, and padding. InFIG. 20, the one MAC header includes n E/T/RAPID subheaders (E/T/RAPIDfields).

Each E/T/RAPID subheader includes an Extension field (E field), a Typefield (T field), and a Random Access Preamble IDentifier field (RAPIDfield). The E field is a flag indicating whether more fields are presentin the MAC header. The E field is set to “1” to indicate that at leastanother set of E/T/RAPID field follows. The E field is set to “0” toindicate that either a MAC RAR or padding starts at the next byte.

The T field is a flag indicating whether the MAC subheader contains aRAPID field and a Backoff Indicator field. The T field is set to “1” toindicate the presence of a RAPID field in the MAC subheader.

The RAPID field identifies the transmitted random access preamble. In acase that the random access preamble transmitted from the terminalapparatus corresponds to the RAPID field, the terminal apparatusdetermines that the reception of the random access response hassucceeded and performs processing on the corresponding MAC RAR.

The MAC RAR includes an R field, a timing advance command field, anuplink grant field, and a Temporary C-RNTI field. The R field is areserved bit set to 0. The timing advance command field indicates anindex value TA used to control the amount of timing adjustment forPUSCH/SRS transmission.

The uplink grant field indicates PUSCH resources used in the uplink. Theuplink grant field has an uplink grant mapped thereto. The TemporaryC-RNTI field indicates the Temporary C-RNTI used by the terminalapparatus in the contention based random access procedure.

The base station apparatus can include information on the PRACH slot inthe random access response corresponding to the second PRACH. Theterminal apparatus can detect the information on the PRACH slot in therandom access response. For example, the information on the PRACH slotmay be included in the R field, may be included in the Timing AdvanceCommand field, may be included in the UL Grant field, or may be includedin the Temporary C-RNTI field. Moreover, a new field including theinformation on the PRACH slot may be included in the random accessresponse. One MAC PDU may include a random access response correspondingto the first PRACH and a random access response corresponding to thesecond PRACH.

Note that the R field may be information identifying an LAA cell orinformation identifying a licensed/unlicensed band.

The first PRACH preamble and the second PRACH preamble can be generatedby an uplink subframe generation unit.

A first PRACH transmission bandwidth W₁ is configured at 6 PRB or 1.08MHz. A second PRACH transmission bandwidth W₂ differs based on thebandwidth W (W=15, 25, 50, 75, or 100 PRB, or 3, 5, 10, 15, or 20 MHz,for example) of the serving cell. For example, the second PRACHtransmission bandwidth W₂ is equal to the bandwidth W of the servingcell or represented by a constant multiple X of the serving cell(W₂=X*W). Alternatively, the second PRACH transmission bandwidth W₂ isrepresented by a value obtained by subtracting a fixed bandwidth Y fromthe bandwidth W of the serving cell (W₂=W−Y). Alternatively, the secondPRACH transmission bandwidth W₂ is configured based on a value in atable associated with the bandwidth of the serving cell. The fixedbandwidth Y may correspond to a PUCCH resource.

The first PRACH preamble includes 139 subcarriers or 839 subcarriers.The second PRACH preamble may include subcarriers other than 139 or 839subcarriers.

The symbol length of the second PRACH preamble may correspond to theOFDM symbol or SC-FDMA symbol length. For example, the symbol length ofthe second PRACH preamble may be equal to the number of OFDM symbolsindicated by any value from 1 to 14.

The symbol length of the first PRACH preamble varies depending on thepreamble format, and the symbol length of the second PRACH preamble maybe determined based on the information included in signalling (RRCsignaling, PDCCH, or the like) from the base station apparatus.

A layer-3 message is a message exchanged between the Radio ResourceControl (RRC) layers of the terminal apparatus and the base stationapparatus and handled in a protocol for a Control-plane (CP (C-Plane)),and may be used synonymously with RRC signaling or RRC message. Aprotocol handling user data (uplink data and downlink data) is referredto as “User-plane (UP (U-Plane))” in contrast to “control plane”. Here,a transport block that is transmission data in the physical layerincludes C-Plane messages and U-Plane data in higher layers. Detaileddescriptions of other physical channels are omitted.

A communicable range (communication area) at each frequency controlledby a base station apparatus is regarded as a cell. Here, thecommunication area covered by the base station apparatus may bedifferent in size and shape for each frequency. Moreover, the coveredarea may be different for each frequency. A radio network, in whichcells having different types of base station apparatuses or differentcell radii are located in a mixed manner in the area with the samefrequency and/or different frequencies to form a single communicationsystem, is referred to as a heterogeneous network.

The terminal apparatus operates by regarding the inside of a cell as acommunication area. In a case that the terminal apparatus moves from acell to a different cell, the terminal apparatus moves to an appropriatedifferent cell through a cell reselection procedure at the time ofhaving no radio connection (during no communication) and through ahandover procedure at the time of having radio connection (duringcommunication). A suitable cell in general indicates a cell that isdetermined that access from the terminal apparatus is not prohibitedbased on information specified by the base station apparatus, and thathas a downlink reception quality satisfying a predefined condition.

Moreover, the terminal apparatus and the base station apparatus mayemploy a technique for aggregating the frequencies (component carriersor frequency band) of multiple different frequency bands through CarrierAggregation and treating the resultant as a single frequency (frequencyband). A component carrier is categorized as an uplink component carriercorresponding to the uplink and a downlink component carriercorresponding to the downlink. In this specification, “frequency” and“frequency band” may be used synonymously.

For example, in a case that each of five component carriers havingfrequency bandwidths of 20 MHz are aggregated through CarrierAggregation, a terminal apparatus capable of performing CarrierAggregation performs transmission and/or reception by assuming that theaggregated carriers have a frequency bandwidth of 100 MHz. Note thatcomponent carriers to be aggregated may have contiguous frequencies orfrequencies some or all of which are discontiguous. For example,assuming that available frequency bands include an 800 MHz band, a 2 GHzband, and a 3.5 GHz band, a component carrier may be transmitted in the800 MHz band, another component carrier ray be transmitted in the 2 GHzband, and yet another component carrier may be transmitted in the 3.5GHz band.

It is also possible to aggregate multiple contiguous or discontiguouscomponent carriers of the same frequency bands. The frequency bandwidthof each component carrier may be narrower (e.g., 5 MHz or 10 MHz) thanthe receivable frequency bandwidth (e.g., 20 MHz) of the terminalapparatus, and the frequency bandwidth of component carriers to beaggregated may be different from each other. Each frequency bandwidthmay be equal to any of the frequency bandwidth of known cells inconsideration of backward compatibility, but may be a frequencybandwidth different from any of the frequency bands of the known cells.

Moreover, component carriers (carrier types) without backwardcompatibility may be aggregated. Note that the number of uplinkcomponent carriers to be allocated to (configured for or added for) theterminal apparatus by the base station apparatus may be the same as ormay be fewer than the number of downlink component carriers.

A cell constituted of an uplink component carrier in which an uplinkcontrol channel is configured for a radio resource request and adownlink component carrier having a cell-specific connection with theuplink component carrier is referred to as “Primary cell (PCell).” Acell constituted of component carriers other than those of the primarycell is referred to as “Secondary cell (SCell).” The terminal apparatusreceives a paging message, detects update of broadcast information,carries out an initial access procedure, configures securityinformation, and the like in a primary cell, and need not perform theseoperations in secondary cells.

Although a primary cell is not a target of Activation and Deactivationcontrols (in other words, considered as being activated at any time), asecondary cell has activated and deactivated states, the change of whichis explicitly specified by the base station apparatus or is made basedon a timer configured for the terminal apparatus for each componentcarrier. The primary cell and secondary cell are collectively referredto as “serving cell”.

Carrier Aggregation achieves communication using multiple componentcarriers (frequency bands) using multiple cells, and is also referred toas cell aggregation. The terminal apparatus may have radio connectionwith the base station apparatus via a relay station device (or repeater)for each frequency. In other words, the base station apparatus of thepresent embodiment may be replaced with a relay station device.

The base station apparatus manages a cell, which corresponds to an areawhere terminal apparatuses can communicate with the base stationapparatus, for each frequency. A single base station apparatus maymanage multiple cells. Cells are classified into multiple types of cellsdepending on the size of the area (cell size) that allows forcommunication with terminal apparatuses. For example, cells areclassified into macro cells and small cells. Moreover, small cells areclassified into femto cells, pico cells, and nano cells depending on thesize of the area. In a case that a terminal apparatus can communicatewith a certain base station apparatus, the cell configured so as to beused for the communication with the terminal apparatus is referred to as“Serving cell” while the other cells not used for the communication arereferred to as “Neighboring cell”, among the cells of the base stationapparatus.

In other words, in carrier-aggregation (also referred to as “carrieraggregation”), multiple serving cells thus configured include a singleprimary cell and one or multiple secondary cells.

A primary cell is a serving cell in which an initial connectionestablishment procedure has been carried out, a serving cell in which aconnection e-establishment procedure has been started, or a cellindicated as a primary cell during a handover procedure. The primarycell operates at a primary frequency. At the point of time when aconnection is (re)established, or later, a secondary cell may beconfigured. Each secondary cell operates at a secondary frequency. Theconnection may be referred to as an RRC connection. For the terminalapparatus supporting CA, a single primary cell and one or more secondarycells are aggregated.

In the present embodiment, Licensed Assisted Access (LAA) is used.According to LAA, an allocated frequency is configured to (used for) theprimary cell, and a non-allocated frequency is configured to at leastone of secondary cells. The secondary cell(s) to which the non-allocatedfrequency is configured is assisted by the primary cell or the secondarycell(s) to which the allocated frequency is configured. For example, theprimary cell or the secondary cell(s) to which the allocated frequencyis configured performs the configuration and/or announces controlinformation by the RRC signaling, MAC signaling and/or PDCCH signalingto the secondary cell(s) to which the non-allocated frequency isconfigured. In the present embodiment, a cell assisted by the primarycell or the secondary cell(s) is also referred to as “LAA cell”. The LAAcell can be aggregated assisted)) with the primary cell and/or thesecondary cell(s) by carrier aggregation. The primary cell or thesecondary cell(s) which assists the LAA cell is also referred to as“assist cell”.

The LAA cell may be aggregated (assisted) by the primary cell and/or thesecondary cell(s) by dual connectivity.

A basic configuration (architecture) of dual connectivity will bedescribed below. For example, the description will be given in a casethat a terminal apparatus 1 connects to multiple base stations 2 (forexample, a base station apparatus 2-1 and a base station apparatus 2-2)at the same time. The base station apparatus 2-1 is a base stationapparatus constituting a macro cell, and the base station apparatus 2-2is a base station apparatus constituting a small cell. The terminalapparatus 1 connecting to the base station apparatuses 2 at the sametime by sing the multiple cells belonging to the multiple base stationapparatuses 2 as described above is referred to as “dual connectivity”.The cells belonging to the respective base station apparatuses 2 may beoperated at the same frequency or different frequencies.

Note that Carrier Aggregation is different from dual connectivity inthat a single one of the base station apparatuses 2 manages multiplecells and the frequencies of the respective cells are different fromeach other. In other words, Carrier Aggregation is a technique forconnecting the single terminal apparatus 1 and a single one of the basestation apparatus 2 via multiple cells having different frequencies,while dual connectivity is a technique for connecting the singleterminal apparatus 1 and the multiple base station apparatuses 2 viamultiple cells having the same frequency or different frequencies.

The terminal apparatus 1 and base station apparatuses 2 can apply atechnique used for Carrier Aggregation, to dual connectivity. Forexample, the terminal apparatus 1 and base station apparatuses 2 mayapply a technique of allocation of a primary cell and secondary cells oractivation/deactivation, to cells connected through dual connectivity.

FIG. 3 is a schematic diagram illustrating an example of a blockconfiguration of a base station apparatus 2 according to the presentembodiment. The base station apparatus 2 includes a higher layer(higher-layer control information notification unit, higher layerprocessing unit) 301, a control unit (base station control unit) 302, acodeword generation unit 303, a downlink subframe generation unit 304,an OFDM signal transmission unit (downlink transmission unit) 306, atransmit antenna (base station transmit antenna) 307, a receive antenna(base station receive antenna) 308, an SC-FDMA signal reception unit(CSI reception unit) 309, and an uplink subframe processing unit 310.The downlink subframe generation unit 304 includes a downlink referencesignal generation unit 305. Moreover, the uplink subframe processingunit 310 includes an uplink control information extraction unit (CSIacquisition unit) 311.

FIG. 4 is a schematic diagram illustrating an example of a blockconfiguration of a terminal apparatus 1 according to the presentembodiment. The terminal apparatus 1 includes a receive antenna(terminal receive antenna) 401, an OFDM signal reception unit (downlinkreception unit) 402, a downlink subframe processing unit 403, atransport block extraction unit (data extraction unit) 405, a controlunit (terminal control unit) 406, a higher layer (higher-layer controlinformation acquisition unit, higher layer processing unit) 407, achannel state measurement unit (CSI generation unit) 408, an uplinksubframe generation unit 409, an SC-FDMA signal transmission unit (UCItransmission unit) 411, and a transmit antenna (terminal transmitantenna) 412. The downlink subframe processing unit 403 includes adownlink reference signal extraction unit 404. Moreover, the uplinksubframe generation unit 409 includes an uplink control informationgeneration unit (UCI generation unit) 410.

First, a flow of downlink data transmission and/or reception will bedescribed with reference to FIG. 3 and FIG. 4. In the base stationapparatus 2, the control unit 302 holds a Modulation and Coding Scheme(MCS) indicating a modulation scheme, a coding rate, and the like in thedownlink, a downlink resource allocation indicating RBs to be used fordata transmission, and information to be used for HARQ control (aredundancy version, an HARQ process number, and a new data indicator)and controls the codeword generation unit 303 and the downlink subframegeneration unit 304, based on these elements. Downlink data (alsoreferred to as a downlink transport block) transmitted from the higherlayer 301 is processed through error correction coding, rate matching,and the like in the codeword generation unit 303 under the control ofthe control unit 302 and then, a codeword is generated. Two codewords atmaximum are transmitted at the same time in a single subframe of asingle cell. The control unit 302 instructs the downlink subframegeneration unit 304 to generate a downlink subframe. First, a codewordgenerated in the codeword generation unit 303 is converted into amodulation symbol sequence through a modulation process, such as PhaseShift Keying (PSK) modulation or Quadrature Amplitude Modulation (QAM).Moreover, a modulation symbol sequence is mapped onto REs of some RBs,and a downlink subframe for each antenna port is generated through aprecoding process. In this operation, the transmission data sequencetransmitted from the higher layer 301 includes higher-layer controlinformation, which is control information about the higher layer (e.g.,dedicated (individual) Radio Resource Control (RRC) signaling).Furthermore, the downlink reference signal generation unit 305 generatesa downlink reference signal. The downlink subframe generation unit 304maps the downlink reference signal to the REs in the downlink subframesin accordance with an instruction from the control unit 302. The OFDMsignal transmission unit 306 modulates the downlink subframe generatedby the downlink subframe generation unit 304 to an OFDM signal, and thentransmits the OFDM signal through the transmit antenna 307. Although aconfiguration of including one OFDM signal transmission unit 306 and onetransmit antenna 307 is illustrated as an example here, a configurationof including multiple OFDM signal transmission units 306 and multipletransmit antennas 307 may be employed for transmitting downlinksubframes through multiple antenna ports. Furthermore, the downlinksubframe generation unit 304 may also have a capability of generatingphysical-layer downlink control channels, such as a PDCCH and an EPDCCHto map the channels to REs in downlink subframes. Multiple base stationapparatuses (base station apparatus 2-1 and base station apparatus 2-2)transmit separate downlink subframes. Note that the base stationapparatus 2 that operates in the LAA cell is configured to include a CCAcheck unit 312 configured to determine whether the channel is idle orbusy. The CCA check unit 312 is implemented with a method fordetermination using power received through the receive antenna 308, amethod for a determination depending on whether a specific signal fromthe uplink subframe processing unit 310 has been detected, and the like.A determination result from the CCA check unit 312 is transmitted to thecontrol unit 302 and used to control the transmission.

In the terminal apparatus 1, an OFDM signal is received by the OFDMsignal reception unit 402 through the receive antenna 401, and an OFDMdemodulation process is performed on the signal. The downlink subframeprocessing unit 403 first detects physical-layer downlink controlchannels, such as a PDCCH and an EPDCCH. More specifically, the downlinksubframe processing unit 403 decodes the signal by assuming that a PDCCHand an EPDCCH have been transmitted in the regions to which the PDCCHand the EPDCCH can be allocated, and checks Cyclic Redundancy Check(CRC) bits added in advance (blind decoding). In other words, thedownlink subframe processing unit 403 monitors a PDCCH and an EPDCCH. Ina case that the CRC bits match an ID (a single terminal-specificidentifier assigned to a single terminal, such as a Cell-Radio NetworkTemporary Identifier (C-RNTI) or a Semi Persistent Scheduling-C-RNTI(SPS-C-RNTI), or a Temporary C-RNTI) assigned by the base stationapparatus beforehand, the downlink subframe processing unit 403recognizes that a PDCCH or an EPDCCH has been detected and extracts aPDSCH by using control information included in the detected PDCCH orEPDCCH. The control unit 406 holds an MCS indicating a modulationscheme, a coding rate, and the like in the downlink based on the controlinformation, a downlink resource allocation indicating RBs to be usedfor downlink data transmission, and information to be used for HARQcontrol, and controls the downlink subframe processing unit 403, thetransport block extraction unit 405, and the like, in accordance withthese elements. More specifically, the control unit 406 performs controlso as to carry out an RE mapping process in the downlink subframegeneration unit 304, an RE demapping process and demodulation processcorresponding to the modulation process, and the like. The PDSCHextracted from the received downlink subframe is transmitted to thetransport block extraction unit 405. Furthermore, the downlink referencesignal extraction unit 404 in the downlink subframe processing unit 403extracts the downlink reference signal from the downlink subframe. Thetransport block extraction unit 405 extracts a transport block that hasbeen subjected to a rate matching process, a rate matching processcorresponding to error correction coding, error correction decoding, andthe like in the codeword generation unit 303, and transmits theextracted transport block to the higher layer 407. The transport blockincludes higher-layer control information, and the higher layer 407notifies the control unit 406 of a necessary physical-layer parameter,based on the higher-layer control information. The multiple base stationapparatuses 2 (base station apparatus 2-1 and base station apparatus2-2) transmit separate downlink subframes, and the terminal apparatus 1receives the downlink subframes. Hence, the above-described processesmay be carried out for the downlink subframe of each of the multiplebase station apparatuses 2. In this situation, the terminal apparatus 1may recognize or may not necessarily recognize that multiple downlinksubframes have been transmitted from the multiple base stationapparatuses 2. In a case that the terminal apparatus 1 does notrecognize the subframes, the terminal apparatus 1 may simply recognizethat multiple downlinks subframes have been transmitted in multiplecells. Moreover, the transport block extraction unit 405 determineswhether the transport block has been detected correctly, and transmits adetermination result to the control unit 406. Note that the terminalapparatus 1 that operates in the LAA cell is configured to include a CCAcheck unit 413 configured to determine whether the channel is idle orbusy. The CCA check unit 413 is implemented with a method fordetermination using power received through the receive antenna 401, amethod for determination depending on whether a specific signal from thedownlink subframe processing unit 403 has been detected, and the like. Adetermination result from the CCA check unit 413 is transmitted to thecontrol unit 406 and used to control the transmission.

Next, a flow of uplink signal transmission and/or reception will bedescribed. In the terminal apparatus 1, the control unit 406 instructs adownlink reference signal extracted by the downlink reference signalextraction unit 404 to be transmitted to the channel state measurementunit 408, and then instructs the channel state measurement unit 408 tomeasure the channel state and/or interference, and further to calculateCSI, based on the measured channel state and/or interference. Thecontrol unit 406 instructs the uplink control information generationunit 410 to generate an HARQ-ACK (DTX (not transmitted yet), ACK(detection success), or NACK (detection failure)) and to map theHARQ-ACK to a downlink subframe, based on a determination result ofwhether the transport block is correctly detected. The terminalapparatus 1 performs these processes on the downlink subframe of each ofmultiple cells. In the uplink control information generation unit 410, aPUCCH including the calculated CSI and/or HARQ-ACK is generated. In theuplink subframe generation unit 409, the PUSCH including the uplink datatransmitted from the higher layer 407 and the PUCCH generated by theuplink control information generation unit 410 are mapped to RBs in anuplink subframe, and an uplink subframe is generated. The uplinksubframe is subjected to the SC-FMA modulation in the SC-FDMA signaltransmission unit 411 to generate an SC-FDMA signal, and the SC-FDMAsignal transmission unit 411 transmits the SC-FDMA signal via thetransmit antenna 412.

Here, the terminal apparatus 1 performs (derives) channel measurementfor calculating the value of the CQI, based on the CRS or the CSI-RS(non-zero power CSI-RS). Whether the terminal apparatus 1 derives thechannel measurement, based on the CRS or the CSI-RS, is determinedaccording to higher layer signalling. Specifically, in a transmissionmode configured with the CSI-RS, the terminal apparatus 1 derives thechannel measurement for calculating the CQI, based only on the CSI-RS.Specifically, in a transmission mode not configured with the CSI-RS, theterminal apparatus 1 derives the channel measurement for calculating theCQI, based on the CRS. The RS used for the channel measurement forcalculating the CSI is also referred to as a first RS.

Here, the terminal apparatus 1 performs (derives) interferencemeasurement for calculating the CQI, based on CSI-IM or a second RS, ina case that this is configured by the higher layer. Specifically, in atransmission mode configured with the CSI-IM, the terminal apparatus 1derives the interference measurement for calculating the CQI, based onthe CSI-IM. Specifically, in the transmission mode configured with theCSI-IM, the terminal apparatus 1 derives the interference measurementfor calculating the value of the CQI corresponding to the CSI process,based only on the CSI-IM resource associated with the CSI process. TheRS or IM used for the channel measurement for calculating the CSI isalso referred to as a second RS.

Note that the terminal apparatus 1 may perform (may derive) theinterference measurement for calculating the CQI, based on the CRS. Forexample, the terminal apparatus 1 may derive the interferencemeasurement for calculating the CQI, based on the CRS, in a case thatthe CSI-IM is not configured.

Note that the channel and/or interference used to calculate the CQI maysimilarly be used as a channel and/or interference for calculating thePMI or RI.

Details of the LAA cell will be described below.

The frequency used by the LAA cell is shared with other communicationsystems and/or other LTE operators. To share the frequency, the LAA cellneeds fairness with the other communication systems and/or the other LTEoperators. For example, a communication method used by the LAA cellneeds a fair frequency sharing technique (method). In other words, theLAA cell is a cell which performs a communication method (communicationprocedure) to which the fair frequency sharing technique is applicable(used).

An example of the fair frequency sharing technique is Listen-Before-Talk(LBT). Before a certain base station or a certain terminal transmits asignal by using a frequency (a component carrier, a carrier, a cell, achannel, or a medium), LBT measures (detects) interference power (aninterference signal, receive power, a receive signal, noise power and anoise signal) or the like of the frequency, to identify (detect, assumeor determine) whether the frequency is in an idle state (a free state, anon-congested state, Absence or Clear) or a busy state (an occupiedstate, a congested state, Presence or Occupied). In a case that thefrequency being in the idle state is identified based on LBT, the LAAcell can transmit a signal at a prescribed timing of the frequency. In acase that the frequency is identified as the busy state, the LAA celldoes not transmit a signal at the prescribed timing of the frequency.LBT controls and prevents an interference with signals to be transmittedby other communication systems and/or other base stations includingother LTE operators and/or terminals. Note that LBT performed by thebase station apparatus before a downlink transmission is referred to asdownlink LBT and that LBT performed by the terminal apparatus before anuplink transmission is referred to as uplink LBT. Furthermore, LBTperformed by the terminal apparatus for sidelink transmissions may bereferred to as sidelink LBT.

An LBT procedure is defined as a mechanism to which Clear ChannelAssessment (CCA) check is applied before a certain base station orterminal uses the frequency (channel). The CCA performs power detectionor signal detection for determining presence or absence of anothersignal in the channel to identify whether the frequency is in the idlestate or the busy state. Note that in the present embodiment, adefinition of CCA may be equivalent to a definition of LBT. Note that,in the present embodiment, CCA is also referred to as carrier sense.Note that the carrier sense may indicate a different mechanism than thatof a carrier sense the performance of which is defined in systems(wireless LAN and the like) other than the LAA used in the non-allocatedfrequency band. For example, the carrier sense in the wireless LAN isassociated with an operation of the terminal apparatus conforming to thewireless LAN standards to detect a radio signal conforming to thewireless LAN standards. Specifically, the carrier sense applied to LAAmay be an operation of detecting a radio signal of a system other thanLAA (or a radio signal conforming to standards), may be an operation ofdetecting a transmit signal of an LAA cell, or may be an operation ofsimply detecting the power (or power strength, power density, receptionstrength, receive signal power, receive signal level, reception level,or the like) in the radio space.

CCA can use various methods as a method for determining the presence orabsence of another signal. For example, CCA makes the determinationbased on whether the interference power at a certain frequency exceeds acertain threshold. Moreover, for example, CCA makes the determinationbased on whether the receive power of a prescribed signal or channel ata certain frequency exceeds a certain threshold. The threshold may bedefined in advance. The threshold may be configured by a base station oranother terminal. The threshold may be determined (configured) based onat least another value (parameter) such as transmit power (maximumtransmit power). Moreover, for example, CCA makes the determination,based on whether a prescribed channel at a certain frequency has beendecoded.

The LBT procedure includes Initial CCA (ICCA, single sensing, LBTcategory 2, Frame-based Equipment (FBE)) allowing a signal to betransmitted after a CCA check is performed once, and Extended CCA (ECCA,multiple sensing, LBT category 3/4, Load-based Equipment (LBE)) allowinga signal to be transmitted after the CCA check is performed a prescribednumber of times. A period in which the CCA check is performed by ICCA isreferred to as an ICCA period or an ICCA slot length, and lasts, forexample, 34 microseconds. Furthermore, a period in which the CCA checkis performed by ECCA is referred to as an ECCA period or an ECCA slotlength, and lasts, for example, 9 microseconds. Note that the prescribednumber of times is also referred to as a backoff counter (counter,random number counter, ECCA counter). Furthermore, a period in which theCCA check is performed after the frequency changes from the busy stateto the idle state is referred to as a defer period or an ECCA deferperiod, and lasts, for example, 34 microseconds.

FIG. 6 illustrates an example of an LBT (LBT category 4, LBE) procedurefor a downlink transmission. In a case that the need arises to transmit,to the terminal apparatus, certain information (data, a buffer, load,traffic) in the downlink while the channel is in the idle state (S601)of waiting for a downlink transmission, the base station apparatusdetermines whether the transmission is needed (S602) and proceeds toinitial CCA (S603). In the initial CCA, the base station apparatusperforms the CCA check during an initial CCA period to sense whether thechannel is idle or busy (S6031). In a case of determining that thechannel is idle as a result of the initial CCA (S603), the base stationapparatus acquires the right to access the channel and proceeds to atransmission operation. Then, the base station apparatus determineswhether to actually perform a downlink transmission at that timing(S604), and in a case of determining to perform the downlinktransmission, the base station apparatus performs the downlinktransmission (S605). After performing the downlink transmission, thebase station apparatus determines whether any information that needsanother downlink transmission is still present (remains) (S606). In acase that no information that needs another downlink transmission hasbeen generated yet (remains), the channel returns to the idle state(S601). On the other hand, in a case that the initial CCA (S603) resultsin the determination that the channel is busy or that the determinationof whether any information that needs another downlink transmission isstill present (remains) (S606) results in the determination thatinformation that needs another downlink transmission is still present(remains), the base station apparatus proceeds to the extended CCA(S607). In the extended CCA, first, the base station apparatus randomlygenerates a counter value N within the range from 0 to q−1 (S6071). Thebase station apparatus then senses whether the channel is idle or busyin the ECCA defer occasion (S6072). In a case of determining that thechannel is busy in the ECCA defer occasion, the base station apparatussenses again whether the channel is idle or busy in the ECCA deferoccasion (6072). On the other hand, in a case of determining that thechannel is idle in the ECCA defer occasion, then the base stationapparatus senses the channel (medium) during one ECCA slot duration(S6073) to determine whether the channel is idle or busy (6074). Thebase station apparatus decrements the counter value N by one (S6075) ina case of determining that the channel is idle, and returns to theprocess of sensing the channel in the ECCA defer occasion (S6072) againin a case of determining that the channel is busy. The base stationapparatus then determines whether the counter value is 0 (S6076), and ina case that the counter value is 0, proceeds to a transmission process(S604, S605). On the other hand, in a case that the counter value is not0, the base station apparatus senses the channel (medium) during oneECCA slot duration again (S6073). Note that, in a case that the countervalue N is generated, a value in a collision window q is updated to avalue from X to Y according to a channel state (S6077).

The value in the collision window q is determined, for example, based onthe HARQ-ACK response in the PDSCH transmitted by the base stationapparatus, a power value obtained by sensing of the channel by the basestation apparatus, reporting of RSRP, RSRQ, and/or RSSI, or the like.The value in the collision window q is, by way of example, exponentiallyincreased. Furthermore, the maximum value X and the minimum value Y usedto determine the value in the collision window q are parametersconfigured by the higher layer.

In the LBT procedure in FIG. 6, the extended CCA may not be performed.Specifically, in a case of determining that the channel is busy as aresult of the initial CCA (S603), the base station apparatus may returnto the idle state (S601) instead of proceeding to the extended CCAprocess (S607). Furthermore, even in a case that, after a downlinktransmission, information that needs another downlink transmission isstill present (S606), the base station apparatus may return to the idlestate (S601) instead of proceeding to the extended CCA process (S607).LBT involving such a process is also referred to as LBT category 2. LBTinvolving such a process may be applied as LBT for a DS transmission, aPDSCH transmission with a time length of 1 ms or shorter, or atransmission only of the PDCCH, for example.

Note that CCA in the LAA cell does not need to be recognized by theterminal connected with (configured to) the LAA cell.

In a case that the terminal apparatus 1 can detect a transmission afterCCA is completed in the LAA cell, the terminal apparatus 1 may assumethat consecutive transmissions are performed for several subframes afterdetection of the first transmission. Several subframes for consecutivetransmissions are also referred to as a transmission burst. Inparticular, several subframes for consecutive PDSCH transmissions arereferred to as a PDSCH transmission burst. The PDSCH transmission burstmay include a channel other than the PDSCH and/or a signal. For example,the PDSCH transmission burst may include the PDSCH and the DS and betransmitted. Moreover, in particular, several subframes for which onlythe DS is transmitted are referred to as a DS transmission burst. Thenumber of subframes for consecutive transmissions through thetransmission burst may be configured for the terminal apparatus 1 byusing an RRC message. In the present embodiment, the transmission burstof the downlink signal or channel is also referred to as a downlinktransmission, and the transmission burst of the uplink signal or channelis also referred to as an uplink transmission.

In a case of detecting a reservation signal included in the beginning ofthe transmission burst, the terminal apparatus can sense thetransmission burst. The terminal apparatus regards several subframesfollowing the subframe in which the reservation signal has beendetected, as a transmission burst. In a case that a firstsynchronization signal, a second synchronization signal, or a thirdsynchronization signal described below is detected, instead of thereservation signal, the terminal apparatus can determine the followingseveral subframes as a transmission burst.

Furthermore, the terminal apparatus can sense a transmission burst in acase of decoding information included in the DCI and relating to asubframe indicating a transmission burst. The DCI is included in thePDCCH or EPDCCH allocated in the CSS for notification. Alternatively,the DCI may be included in the PDCCH or EPDCCH allocated in the USS fornotification.

The LAA cell may be defined as a cell different from a secondary cellwhich uses the allocated frequency. For example, the LAA cell isconfigured differently from the configuration of the secondary cellwhich uses the allocated frequency. Part of parameters configured to theLAA cell is not configured to the secondary cell which uses theallocated frequency. Part of the parameters configured to the secondarycell which uses the allocated frequency is not configured to the LAAcell. In the present embodiment, the LAA cell is described as a celldifferent from the primary cell and the secondary cell(s), but the LAAcell may be defined as one of the secondary cells. Secondary cells ofthe related art are also referred to as “first secondary cells”, and theLAA cell is also referred to as “second secondary cell”. A primary celland secondary cell(s) of the related art are also referred to as “firstserving cells”, and the LAA cell is also referred to as “second servingcell”.

The LAA cell may be different from a frame structure type of the relatedart. For example, a first frame structure type (FS1, FDD, framestructure type 1) or a second frame structure type (FS2, TDD, framestructure type 2) are used for (configured to) the serving cells in therelated art, and a third frame structure type (frame structure type 3,FS3) is used for (configured to) the LAA cell. Note that either an LAAcell of the first frame structure type or an LAA cell of the secondframe structure type may be used (may be configured).

The first frame structure type is applied to the Frequency DivisionDuplex (FDD). In other words, FS1 is applied to a cell operationsupporting the FDD. FS1 is applicable to both the Full Duplex-FDD(FD-FDD) and the Half Duplex-FDD (HD-FDD). In the FDD, 10 subframes canbe used for each of downlink transmission and uplink transmission. Inthe FDD, the downlink transmission and the uplink transmission areseparated in the frequency domain. In other words, different carrierfrequencies are used for the downlink transmission and the uplinktransmission. In an HD-FDD operation, the terminal apparatus cannotperform transmission and reception at the same time, but in an FD-FDDoperation, the terminal apparatus can perform transmission and receptionat the same time.

Moreover, HD-FDD has two types: for a type A HD-FDD operation, a guardperiod is created by a terminal apparatus by not receiving the last part(last symbol) of a downlink subframe immediately before an uplinksubframe from the same terminal apparatus; and for a type B HD-FDDoperation, guard periods, each referred to as an HD guard subframe, arecreated by a terminal apparatus by not receiving a downlink subframeimmediately before an uplink subframe from the same terminal apparatus,and by not receiving a downlink subframe immediately after an uplinksubframe from the same terminal apparatus. That is, in the HD-FDDoperation, a guard period is created by the terminal apparatuscontrolling a reception process of the downlink subframe. The symbolsmay include either OFDM symbols or SC-FDMA symbols.

The second frame structure type is applied to Time Division Duplex(TDD). In other words, FS2 is applied to a cell operation supporting theTDD. Each radio frame includes two half-frames. Each half-frame includesfive subframes. The UL-DL configuration in a certain cell may be changedfor each radio frame. The subframe in uplink or downlink transmissionmay be controlled in the latest radio frame. The terminal apparatus canacquire the UL-DL configuration in the latest radio frame via a PDCCH orhigher layer signalling. Note that the UL-DL configuration indicates aconstitution of an uplink subframe, a downlink subframe, and a specialsubframe, in TDD. The special subframe includes a Downlink Pilot TimeSlot (DwPTS) enabling downlink transmission, a guard period (GP), and anUplink Pilot Time Slot (UpPTS) in which uplink transmission is possible.The configurations of the DwPTS and the UpPTS in the special subframeare managed in a table, so that the terminal apparatus can acquire theconstitution via higher layer signalling. Note that the special subframeserves as a switch point from downlink to uplink. Specifically, at theswitching point, the terminal apparatus changes from reception totransmission, and the base station apparatus changes from transmissionto reception. The switching point may have a 5 ms cycle and a 10 mscycle. In a case that a switching point has a 5 ms cycle, the specialsubframe exists in both half frames. In a case that a switching pointhas a 10 ms cycle, the special subframe exists only in a first halfframe.

The Normal Cyclic Prefix (NCP) and the Extended Cyclic Prefix (ECP) areapplied to FS1 and FS2.

The third frame structure type is applied to a Licensed Assisted Access(LAA) secondary cell operation. Alternatively, only the NCP may beapplied to FS3. 10 subframes included in the radio frame are used fordownlink transmission. The terminal apparatus performs processing on asubframe as an empty subframe without assuming that a signal exists inthe subframe, unless otherwise specified or as long as downlinktransmission is not detected in the subframe. Downlink transmissionexclusively uses one or multiple consecutive subframes. The consecutivesubframes include the first subframe and the last subframe. The firstsubframe starts from any symbol or slot (e.g., OFDM symbol #0 or #7) ofthe subframe. In the last subframe, the full subframe or the number ofsymbols based on one DwPTS duration is exclusively used. Note thatwhether the certain subframe in the consecutive subframes is the lastsubframe is indicated to the terminal apparatus by using a certain fieldincluded in the DCI format. The field may further indicate the subframein which the field has been detected or the number of OFDM symbols usedin the next subframe. In the FS3, the base station apparatus performs achannel access procedure associated with the LBT before downlinktransmission.

The terminal apparatus and the base station apparatus supporting the FS3may perform communication in a frequency band requiring no license.

The operating band corresponding to the LAA or FS3 cell may be managedtogether with a table of the EUTRA operating band. For example, theindices for the EUTRA operating band are managed using 1 to 44, and theindex for the operating band corresponding to the LAA (or LAA frequency)is managed using 46. For example, in the case of index 46, only thedownlink frequency band may be defined. In the case of some of theindices, the uplink frequency band may be reserved in advance as isreserved or will be defined later. Moreover, corresponding duplex modemay be a duplex mode different from FDD or TDD or may be FDD or TDD. Thefrequency in which the LAA operation is possible is preferably 5 GHz orhigher but may be 5 GHz or lower. In other words, as the operating bandcorresponding to the LAA, LAA operation communication may be performedin the associated frequency.

Moreover, the third frame structure type may be preferably a framestructure type corresponding to a TDD cell that can performtransmissions at the same frequency both in the uplink and in thedownlink while having characteristics of an FDD cell. For example, thethird frame structure type may have uplink subframes, downlinksubframes, and special subframes but may be similar to the FDD cell interms of an interval from reception of the uplink grant until atransmission of the PUSCH scheduled in the uplink grant or an intervalfrom reception of the PDSCH to HARQ feedback to the PDSCH.

Furthermore, the third frame structure type may be preferably a framestructure type independent of a TDD uplink/downlink (TDD UL/DL)configuration in the related art. For example, the uplink subframes, thedownlink subframes, and the special subframes may be aperiodicallyconfigured for the radio frame. For example, the uplink subframes, thedownlink subframes, and the special subframes may be determined based onthe PDCCH or the EPDCCH.

Here, the non-allocated frequency is a frequency different from theallocated frequency that is allocated as a dedicated frequency to aprescribed operator. For example, the non-allocated frequency is afrequency used by a wireless LAN. For example, the non-allocatedfrequency is a frequency which is not configured to the LTE in therelated art, and the allocated frequency is a frequency which can beconfigured by the LIE in the related art. In the present embodiment, thefrequency configured to the LAA cell is described as the non-allocatedfrequency, but is not limited to this. In other words, the non-allocatedfrequency can be replaced with a frequency configured to the LAA cell.For example, the non-allocated frequency is a frequency which cannot beconfigured to the primary cell, and is a frequency which can beconfigured only to the secondary cell(s). For example, the non-allocatedfrequency includes a frequency shared with multiple operators. Forexample, the non-allocated frequency is a frequency which is configuredonly to a cell configured, assumed and/or processed differently from theprimary cell or secondary cell(s) of the related art.

The LAA cell may be a cell which uses a different method from the methodof the related art for structures of radio frames, physical signalsand/or physical channels according to LTE, and a communicationprocedure.

For example, in the LAA cell, prescribed signals and/or channelsconfigured (transmitted) by the primary cell and/or the secondarycell(s) are not configured (transmitted). The prescribed signals and/orchannels include the CRS, the DS, the PDCCH, the EPDCCH, the PDSCH, thePSS, the SSS, the PBCH, a PHICH, a PCFICH, the CSI-RS and/or an SIB, orthe like. For example, the signals and/or the channels that are notconfigured in the LAA cell are as follows. In addition, the signalsand/or the channels described below may be used in combination. Notethat in the present embodiment, the signals and/or the channels that arenot configured in the LAA cell may also be read as signals and/orchannels whose the transmissions from the LAA cell are not expected bythe terminal.

(1) In the LAA cell, control information of a physical layer is nottransmitted on the PDCCH, but is transmitted only on the EPDCCH.

(2) In the LAA cell, the CRS, the DMRS, the URS, the PDCCH, the EPDCCHand/or the PDSCH are not transmitted in subframes which are activated(on-state) or all subframes, and the terminal does not assume thistransmission in all subframes.

(3) In the LAA cell, the terminal assumes transmission of the DSs, thePSSs and/or the SSSs in subframes which are activated (on-state).

(4) In the LAA cell, information of CRS mapping is announced to theterminal for each subframe, and the terminal assumes the CRS mappingbased on the information. For example, according to the assumption ofthe CRS mapping, the CRS is not mapped onto all resource elements of thecorresponding subframe. According to the assumption of the CRS mapping,the CRS is not mapped onto part of resource elements (e.g., all resourceelements in two head OFDM symbols) of the corresponding subframe.According to the assumption of the CRS mapping, the CRSs are mapped ontoall resource elements of the corresponding subframe. For example, theinformation of the CRS mapping is announced from the corresponding LAAcell or a cell different from the corresponding LAA cell. Theinformation of the CRS mapping is included in the DCI and is announcedon the PDCCH or the EPDCCH.

For example, in the LAA cell, the prescribed signals and/or channelswhich is not configured (transmitted) by the primary cell and/or thesecondary cell(s) is configured (transmitted).

For example, in the LAA cell, only downlink component carrier orsubframe is defined, and only downlink signal and/or channel aretransmitted. In other words, in the LAA cell, uplink component carrieror subframe is not defined, and uplink signal and/or channel is nottransmitted.

For example, in the LAA cell, a Downlink Control Information (DCI)format which can be supported is different from a DCI format which cansupport the primary cell and/or the secondary cell(s). The DCI formatwhich supports only the LAA cell is defined. The DCI format whichsupports the LAA cell includes control information which is only validfor the LAA cell.

The terminal apparatus can recognize the LAA cell, based on a parameterprovided by the higher layer. For example, the terminal apparatus canrecognize a cell (band) in the related art or the LAA cell (LAA band),based on a parameter indicative of the center frequency of the componentcarrier. In this case, information about the center frequency isassociated with the type of the cell (band).

For example, in the LAA cell, the assumption of the signals and/orchannels is different from the secondary cells in the related art.

First, the assumption of the signals and/or channels in the secondarycells of the related art will be described. A terminal that satisfiespart or all of the following conditions assumes that the PSS, the SSS,the PBCH, the CRS, the PCFICH, the PDSCH, the PDCCH, the EPDCCH, thePHICH, the DMRS and/or the CSI-RS may not be transmitted by thesecondary cell except transmission of the DS. The terminal assumes thatthe DS is always transmitted by the secondary cell. The assumptioncontinues to a subframe in which an activation command (a command foractivation) is received by the terminal in the secondary cell at acertain carrier frequency.

(1) The terminal supports a configuration (parameter) associated withthe DS.

(2) RRM measurements based on the DS is configured to the terminal inthe secondary cell.

(3) The secondary cell is deactivated (deactivated state).

(4) Reception of the MBMS by a higher layer is not configured to theterminal in the secondary cell.

Furthermore, in a case that the secondary cell is activated (activatedstate), the terminal assumes that the PSS, the SSS, the PBCH, the CRS,the PCFICH, the PDSCH, the PDCCH, the EPDCCH, the PHICH, the DMRS and/orthe CSI-RS are transmitted by the secondary cell in a configuredprescribed subframe or all subframes.

Next, an example of the assumption of the signals and/or channels in theLAA cell will be described. A terminal that satisfies part or all of thefollowing conditions assumes that the PSS, the SSS, the PBCH, the CRS,the PCFICH, the PDSCH, the PDCCH, the EPDCCH, the PHICH, the DMRS and/orthe CSI-RS may not be transmitted together with transmission of the DSby the LAA cell. The assumption continues to subframe in which anactivation command (a command for activation) is received by theterminal in the secondary cell at a certain carrier frequency.

(1) The terminal supports a configuration (parameter) associated withthe DS.

(2) RRM measurements based on the DS is configured to the terminal inthe LAA cell.

(3) The LAA cell is deactivated (deactivated state).

(4) Reception of the MBMS by a higher layer is not configured to theterminal in the LAA cell.

Furthermore, another example of the assumption of the signals and/orchannels in the LAA cell will be described. In a case that the LAA cellis deactivated (deactivated state), the assumption of the signals and/orchannels in the LAA cell is the same as the assumption of the signalsand/or channels in the secondary cells in the related art. In a casethat the LAA cell is activated (activated state), the assumption of thesignals and/or channels in the LAA cell is different from the assumptionof the signals and/or channels in the secondary cells in the relatedart. In a case that, for example, the LAA cell is activated (activatedstate), the terminal assumes that the LAA cell may not transmit the PSS,the SSS, the PBCH, the CRS, the PCFICH, the PDSCH, the PDCCH, theEPDCCH, the PHICH, the DMRS and/or the CSI-RS except a prescribedsubframe configured to the LAA cell. Details will be described below.

Furthermore, the description has been given of a case that CCA isperformed on one subframe, but a time (period) for performing CCA is notlimited to this. The period for performing CCA may vary per LAA cell,per CCA timing, or per execution of CCA. For example, CCA is performedat a time based on a prescribed time slot (a time interval or a timedomain). This prescribed time slot may be defined or configured based ona time obtained by dividing one subframe by the prescribed number. Theprescribed time slot may be determined or configured by the prescribednumber of subframes.

Furthermore, in the present embodiment, a field size in the time domainsuch as a time (time slot) for performing CCA or a time in which thechannel and/or signal are transmitted (can be transmitted) in a certainsubframe can be expressed by using a prescribed time unit. For example,the field size in the time domain is expressed by some time units Ts. Tsis 1/(15000×2048) seconds. For example, one subframe time is 30720×Ts(one millisecond). For example, one ICCA slot length or defer period is1044×Ts (approximately 33.98 microseconds) or 1045×Ts (approximately34.02 microseconds). For example, one ECCA slot length is 276×Ts(approximately 8.984 microseconds) or 277×Ts (approximately 9.017microseconds). For example, one ECCA slot length is 307×Ts(approximately 9.993 microseconds) or 308×Ts (approximately 10.03microseconds).

Furthermore, whether the LAA cell can transmit the channel and/or signal(including the reservation signal) from an intermediate symbol in acertain subframe may be configured for the terminal or the LAA cell. Forexample, information indicating whether such transmission is possible inthe configuration on the LAA cell is configured to the terminal by theRRC signaling. The terminal switches processing associated withreception (monitoring, recognition, and decoding) at the LAA cell, basedon the information.

Furthermore, subframes in which symbols can be transmitted from anintermediate symbol (also including subframes in which symbols up to theintermediate symbol can be transmitted) may be all subframes in LAAcell. Furthermore, subframes in which symbols can be transmitted fromthe intermediate symbol may be subframes defined in advance for the LAAcell or configured subframes.

Furthermore, subframes in which symbols can be transmitted from theintermediate symbol (also including subframes in which symbols up to theintermediate symbol can be transmitted) can be configured, announced ordetermined based on an Uplink/Downlink configuration (UL/DLconfiguration) according to TDD. For example, such subframes aresubframes announced (designated) as special subframes by the UL/DLconfiguration. Each of the special subframes in the LAA cell is asubframe including at least one of the three fields, a Downlink PilotTime Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot(UpPTS). The configuration on the special subframe in the LAA cell maybe configured or announced by the RRC signaling or PDCCH or EPDCCHsignaling. This configuration configures a length in time of at leastone of the DwPTS, the GP and the UpPTS. Furthermore, this configurationis index information indicating candidates of the predetermined lengthin time. Furthermore, for this configuration, the same length in time asthe DwPTS, the GP and the UpPTS used for the special subframeconfiguration configured to the TDD cells in the related art can beused. In other words, the length in time in which transmission ispossible in a certain subframe is determined based on one of the DwPTS,the GP and the UpPTS.

Further, in the present embodiment, the reservation signal may be asignal that can be received by a LAA cell different from the LAA cellthat transmits the reservation signal. For example, the LAA celldifferent from the LAA cell that transmits the reservation signal is theLAA cell (neighboring LAA cell) neighboring to the LAA cell thattransmits the reservation signal. For example, the reservation signalincludes information of a transmission state (use state) of a prescribedsubframe and/or symbol in the LAA cell. In a case that the LAA celldifferent from the LAA cell that transmits a certain reservation signalreceives the reservation signal, the LAA cell having received thereservation signal recognizes the transmission state of the prescribedsubframe and/or symbol, based on the reservation signal, and performsscheduling according to the state.

Furthermore, the LAA cell having received the reservation signal mayperform LBT before transmitting a channel and/or signal. This LTB isperformed based on the received reservation signal. For example, duringthis LBT, the channels and/or the signals transmitted (assumed to betransmitted) from the LAA cell having transmitted the reservation signalare taken into consideration, and scheduling including resourceallocation and MCS selection is performed.

Furthermore, in a case that the LAA cell having received the reservationsignal performs scheduling of transmitting the channels and/or signals,based on the reservation signal, it is possible to announce informationof such scheduling to one or more LAA cells including the LAA cellhaving transmitted this reservation signal according to a prescribedmethod. For example, the prescribed method is a method for transmittingthe prescribed channel and/or signal including the reservation signal.Furthermore, for example, the prescribed method is a method forperforming announcement via a backhaul such as an X2 interface.

Furthermore, according to carrier aggregation and/or dual connectivity,a terminal of the related art can configure up to five serving cells.However, the terminal according to the present embodiment can extend amaximum number of serving cells that can be configured. In other words,the terminal according to the present embodiment can configure more thanfive serving cells. For example, the terminal according to the presentembodiment can configure up to 16 or 32 serving cells. For example, themore than five serving cells configured by the terminal according to thepresent embodiment include the LAA cell. Furthermore, all of the morethan five serving cells configured by the terminal according to thepresent embodiment may be the LAA cell.

Furthermore, in a case that the more than five serving cells can beconfigured, a configuration on part of the serving cells may bedifferent from the configuration of the serving cells in the related art(i.e., the secondary cell(s) in the related art). For example,differences of this configuration are as follows. The configurationsdescribed below may be used in combination.

(1) To the terminal, up to five serving cells in the related art areconfigured, and up to 11 or 27 serving cells different from servingcells in the related art are configured. In other words, to theterminal, in addition to a primary cell of the related art, up to foursecondary cells of the related art are configured, and up to 11 or 27secondary cells different from the secondary cells of the related artare configured.

(2) The configuration on the serving cells (secondary cells) differentfrom the serving cells of the related art includes configurations on anLAA cell. For example, to the terminal, in addition to the primary cellin the related art, up to four secondary cells that do not include theconfiguration on the LAA cell are configured, and up to 11 or 27secondary cells different from the secondary cells in the related artare configured.

Furthermore, in a case that the more than five serving cells can beconfigured, the base station (including the LAA cell) and/or theterminal can perform different processing or assumption compared to thecase that up to five serving cells are configured. For example,differences of the processing and assumption are as follows. Theprocessing or the assumption described below may be used in combination.

(1) Even in the case that the more than five serving cells areconfigured, the terminal assumes that the PDCCH, the EPDCCH and/or thePDSCH are simultaneously transmitted (received) from the five servingcells at maximum. Consequently, the terminal can use the same method asthe method of the related art, for reception of the PDCCH, the EPDCCHand/or the PDSCH and transmission of HARQ-ACK for the PDSCH.

(2) In the case that the more than five serving cells are configured, acombination (group) of cells for bundling of HARQ-ACKs for the PDSCHs inthese serving cells are configured to the terminal. For example, allserving cells, all secondary cells, all LAA cells or all secondary cellsdifferent from the secondary cells in the related art includeinformation (configuration) on bundling of HARQ-ACKs between the servingcells. For example, the information of the bundling of HARQ-ACKs betweenthe serving cells is an identifier (an index or an ID) for performingthe bundling. For example, the bundling is performed on the HARQ-ACKsover cells having the same identifier to be bundled. This bundling isperformed according to a logical AND operation fort the targetHARQ-ACKs. Furthermore, the maximum number of identifiers to be bundledcan be five. Furthermore, the maximum number of identifiers to bebundled can be five including the number of cells that does not performbundling. In other words, the number of groups to perform bundling overthe serving cells can be five at maximum. Consequently, the terminal canuse the same method as the method of the related art, for reception ofthe PDCCH, the EPDCCH and/or the PDSCH and transmission of HARQ-ACK forthe PDSCH.

(3) In the case that the more than five serving cells are configured, acombination (group) of cells for multiplexing of HARQ-ACKs for thePDSCHs in these serving cells are configured to the terminal. In thecase that the combination (group) of the cells for multiplexing of theHARQ-ACKs for the PDSCHs is configured, the multiplexed HARQ-ACKs aretransmitted on the PUCCH or the PUSCH, based on the group. The maximumnumber of serving cells to be multiplexed is defined or configured foreach group. The maximum number is defined or configured based on themaximum number of serving cells configured to the terminal. For example,the maximum number is the same as the maximum number of serving cellsconfigured to the terminal, or half the maximum number of serving cellsconfigured to the terminal. Furthermore, the maximum number of PUCCHs tobe simultaneously transmitted is defined or configured based on themaximum number of serving cells to be multiplexed in each group and themaximum number of serving cells configured to the terminal.

In other words, the number of configured first serving cells (i.e., theprimary cell and/or the secondary cell(s)) is a prescribed number (i.e.,five) or less. A total of the configured first serving cells and secondserving cell (i.e., LAA cell) exceeds the prescribed number.

Next, terminal capability associated with LAA will be described. Theterminal announces (transmits) information (terminal capability) oncapability of the terminal to the base station by the RRC signaling,based on a command from the base station. The terminal capability of acertain function (feature) is announced (transmitted) in a case that thefunction (feature) is supported, and is not announced (transmitted) in acase that the function (feature) is not supported. Furthermore, theterminal capability of the certain function (feature) may be informationindicating whether testing and/or mounting this function (feature) hasbeen finished. For example, the terminal capability according to thepresent embodiment is as follows. The terminal capability describedbelow may be used in combination.

(1) The terminal capability associated with support of the LAA cell, andthe terminal capability associated with support of a configuration ofmore than five serving cells are independently defined. For example, theterminal that supports the LAA cell supports the configuration of themore than five serving cells. In other words, the terminal that does notsupport the configuration of the more than five serving cells does notsupport the LAA cell. In this case, the terminal that supports theconfiguration of the more than five serving cells may or may not supportthe LAA cell.

(2) The terminal capability associated with support of the LAA cell, andthe terminal capability associated with support of a configuration ofmore than five serving cells are independently defined. For example, theterminal that supports the configuration of the more than five servingcells supports the LAA cell. In other words, the terminal that does notsupport the LAA cell does not support the configuration of the more thanfive serving cells. In this case, the terminal that supports the LAAcell may or may not support the configuration of the more than fiveserving cells.

(3) The terminal capability associated with downlink in the LAA cell,and the terminal capability associated with uplink in the LAA cell areindependently defined. For example, the terminal that supports theuplink in the LAA cell supports the downlink in the LAA cell. In otherwords, the terminal that does not support the downlink in the LAA celldoes not support the uplink in the LAA cell. In this case, the terminalthat supports the downlink in the LAA cell may or may not support theuplink in the LAA cell.

(4) The terminal capability associated with support of the LAA cellincludes support of a transmission mode configured only to the LAA cell.

(5) The terminal capability associated with the downlink according tothe configuration of the more than five serving cells, and the terminalcapability associated with the uplink according to the configuration ofthe more than five serving cells serving cells are independentlydefined. For example, the terminal that supports the uplink according tothe configuration of the more than five serving cells supports thedownlink according to the configuration of the more than five servingcells. In other words, the terminal that does not support the downlinkaccording to the configuration of the more than five serving cells doesnot support the uplink according to the configuration of the more thanfive serving cells. In this case, the terminal that supports thedownlink according to the configuration of the more than five servingcells may or may not support the uplink according to the configurationof the more than five serving cells.

(6) Regarding the terminal capability according to the configuration ofthe more than five serving cells, terminal capability that supports aconfiguration of 16 downlink serving cells (component carriers) atmaximum, and terminal capability that supports a configuration of 32downlink serving cells at maximum are independently defined.Furthermore, the terminal that supports the configuration of 16 downlinkserving cells at maximum supports the configuration of at least oneuplink serving cell. The terminal that supports the configuration of 32downlink serving cells at maximum supports the configuration of at leasttwo uplink serving cells. That is, the terminal that supports theconfiguration of 16 downlink serving cells at maximum may not supportthe configuration of two or more uplink serving cells.

(7) The terminal capability associated with the support of the LAA cellis announced based on a frequency (band) used by the LAA cell. In a casethat, for example, the terminal announces a supported frequency or afrequency combination, and the announced frequency or frequencycombination includes at least one frequency used by the LAA cell, theterminal implicitly announces that this terminal supports the LAA cell.In other words, in a case that the announced frequency or frequencycombination does not include the frequency used by the LAA cell at all,the terminal implicitly announces that this terminal does not supportthe LAA cell.

(8) The terminal capability associated with uplink in the LAA cell andthe terminal capability associated with second PRACH preambletransmission are independently defined. For example, in a case that theterminal apparatus supports second PRACH preamble transmission, theterminal apparatus supports uplink transmission. In other words, theterminal apparatus not supporting uplink transmission does not supportsecond PRACH preamble transmission. In this case, the terminal apparatussupporting uplink transmission may support but need not support secondPRACH preamble transmission.

Furthermore, the present embodiment has described a case where the LAAcell transmits the PDCCH or the EPDCCH for announcing the DCI for thePDSCH transmitted from this LAA cell (i.e., a case of self scheduling),but is not limited to this. The method described in the presentembodiment is applicable also in a case that, for example, a servingcell different from the LAA cell transmits the PDCCH or the EPDCCH forannouncing the DCI for the PDSCH transmitted from the LAA cell (i.e., acase of cross carrier scheduling).

Furthermore, in the present embodiment, the information for recognizingthe symbols in which the channels and/or signals are transmitted may bebased on the symbols in which the channels and/or signals are nottransmitted. For example, this information is information indicating thelast symbol of the symbols in which the channels and/or signals are nottransmitted. Furthermore, the information for recognizing the symbols inwhich the channels and/or signals are transmitted may be determinedbased on other information or parameters.

Furthermore, in the present embodiment, the symbols in which thechannels and/or signals are transmitted may be independently configured(announced or defined) to the channels and/or signals. In other words,the information for recognizing the symbols in which the channels and/orsignals are transmitted, and the announcement method of the informationcan be independently configured (announced or defined) to the channelsand/or signals. For example, the information for recognizing the symbolsin which the channels and/or signals are transmitted, and theannouncement method of the information may be independently configured(announced or defined) for the PDSCH and the EPDCCH.

Furthermore, in the present embodiment, symbols/subframes in which thechannels and/or signals are not transmitted (cannot be transmitted) maybe symbols/subframes in which the channels and/or signals are notassumed to be transmitted (be able to be transmitted) from a viewpointof the terminal. That is, the terminal can regard that the LAA cell doesnot transmit the channels and/or signals in the symbols/subframes.

Furthermore, in the present embodiment, the symbols/subframes in whichthe channels and/or signals are transmitted (can be transmitted) may besymbols/subframes in which the channels and/or signals may be assumed tobe transmitted from the viewpoint of the terminal. In other words, theterminal can regard that the LAA cell may or may not transmit thechannels and/or signals in the symbols/subframes.

Furthermore, in the present embodiment, the symbols/subframes in whichthe channels and/or signals are transmitted (can be transmitted) may besymbols/subframes in which the channels and/or signals are assumed to besurely transmitted from the viewpoint of the terminal. That is, theterminal can regard that the LAA cell surely transmits the channelsand/or signals in the symbols/subframes.

Next, an example of a configuration of a downlink reference signal inthe LAA cell will be described.

FIG. 5 is a diagram illustrating an example of the configuration of thedownlink reference signal. By way of example, the CRSs can be mapped toREs R0 to R3. R0 denotes examples of the REs on which the CRS of antennaport 0 is mapped, R1 denotes examples of the REs on which the CRS ofantenna port 1 is mapped, R2 denotes examples of the REs on which theCRS of antenna port 2 is mapped, and R3 denotes examples of the REs onwhich the CRS of antenna port 3 is mapped. Note that the CRSs may beshifted, for mapping, in the frequency direction according to aparameter associated with the cell identity. Specifically, an index kfor which the RE specifies mapping is increased based on a value ofN^(cell) _(ID) mod 6. Here, N^(cell) _(ID) denotes the value of thephysical cell identity. The DMRSs can be mapped to REs D1 and D2. D1denotes examples of the REs on which the DMRSs of antenna ports 7, 8,11, 13 are mapped, and D2 denotes examples of the REs on which the DMRSsof antenna ports 9, 10, 12, 14 are mapped. The CSI-RSs can be mapped toREs C1 to C4. C0 denotes examples of the REs on which the CSI-RSs ofantenna ports 15, 16 are mapped, C1 denotes examples of the REs on whichthe CSI-RSs of antenna ports 17, 18 are mapped, C2 denotes examples ofthe REs on which the CSI-RSs of antenna ports 19, 20 are mapped, and C3denotes examples of the REs on which the CSI-RSs of antenna ports 21, 22are mapped. Note that the CSI-RS may be mapped to the RE at OFDM symbol#5 or #6 in slot 0 and to the RE at OFDM symbol #1, #2, or #3 in slot 1.The REs on which the CSI-RS is mapped are indicated based on a parameterprovided by the higher layer.

Next, the relationship between a downlink transmission, an uplinktransmission, and LBT will be described.

FIG. 7 illustrates an example of the relationship between the intervalbetween a downlink transmission and an uplink transmission and types ofLBT on the time axis according to the present embodiment. In (a) of FIG.7, a case where the downlink transmission and the uplink transmissionare sufficiently distant from each other on the time axis isillustrated. In the case where the downlink transmission and the uplinktransmission are sufficiently distant from each other, for example, theinterval between the downlink transmission and the uplink transmissionis at least one subframe (1 millisecond). In such a case, there is nochannel state (channel sensing result) correlation between the downlinktransmission and the uplink transmission, thus leading to the need toperform LBT involving sufficient carrier sensing on each transmission.Here, LBT performed before the uplink transmission in (a) of FIG. 7 isreferred to as first uplink LBT. In (b) of FIG. 7, a case where thedownlink transmission and the uplink transmission are slightly distantfrom each other on the time axis is illustrated. In the case where thedownlink transmission and the uplink transmission are slightly distantfrom each other, for example, the interval between the downlinktransmission and the uplink transmission corresponds to several symbols(several tens of microseconds to several hundred microseconds). In sucha case, CCA performed before the downlink transmission may be consideredto allow the channel state (channel sensing result) to be alsomaintained before the uplink transmission. Thus, the terminal apparatusmay perform simplified CCA before transmitting an uplink signal. Here,LBT performed before the uplink transmission in (b) of FIG. 7 isreferred to as second uplink LBT. In (c) of FIG. 7, a case where thedownlink transmission and the uplink transmission are not substantiallydistant from each other on the time axis is illustrated. In the casewhere the downlink transmission and the uplink transmission are notsubstantially distant from each other, for example, the interval betweenthe downlink transmission and the uplink transmission is severalmicroseconds to several tens of microseconds, such as 34 microseconds or40 microseconds. In such a case, a channel is reserved for the uplinktransmission by the downlink transmission, and thus, the downlinktransmission and the uplink transmission may be regarded as onetransmission burst. Thus, the terminal apparatus may perform an uplinktransmission without performing CCA. As in these examples, the uplinksignal and/or channel can be efficiently transmitted also in the LAAcell by changing the LBT procedure to be performed, according to theinterval between the downlink transmission and the uplink transmission.

The uplink transmission and the downlink transmission in FIG. 7 may beinterchanged with each other. In other words, downlink LBT may beomitted in a case that the uplink transmission and the downlinktransmission are not substantially distant from each other on the timeaxis.

A procedure for uplink LBT relating to PRACH preamble transmission willbee described below.

The base station apparatus can reserve in advance one or multiple PRACHresources for the terminal apparatus. The PRACH resource that the basestation apparatus reserves for the terminal apparatus is referred toalso as a reservation resource below. The base station apparatus mayreserve the same PRACH resource for the terminal apparatuses in a cellor may reserve different PRACH resources in a terminal apparatus groupconstituted by one or multiple terminal apparatuses. The base stationapparatus can notify the terminal apparatus of information on thereservation resource by including the reservation resource in PDCCH, RRCsignaling, PDSCH, PBCH, MIB, SIB, or the like.

The terminal apparatus can perform uplink LBT in part of or all theresources reserved for PRACH, based on the reservation resource notifiedby the base station apparatus. In a case that the terminal apparatusperforms PRACH preamble transmission by using the PRACH resource (thePRACH resource may be a term including the reservation resource, in thepresent embodiment), the PRACH preamble transmission may be performedbased on uplink LBT.

In a case that the terminal apparatus performs PRACH preambletransmission by using the PRACH resource, the PRACH preambletransmission may be performed without being based on uplink LBT. Inparticular, in a case that the terminal apparatus performs PRACHpreamble transmission by using the reservation resource, the PRACHpreamble transmission may be performed without being based on uplinkLBT.

FIG. 21 is a diagram illustrating an example of reservation resourcesconfigured for terminal apparatuses.

In the example illustrated in FIG. 21, the first slot (indicated in agrid pattern) of the multiple PRACH slots in the PRACH resource isallocated to a terminal apparatus 1-A (allocated to a reservationresource 1-A), the third. PRACH slot (indicated by oblique lines) isallocated to the terminal apparatus 1-B (allocated to a reservationresource 1-B), the fourth PRACH slot (indicated by vertical lines) isallocated to a terminal apparatus 1-C (allocated to a reservationresource 1-C). For example, in a case that the terminal apparatus 1-Cperforms CCA, the terminal apparatus 1-C can perform CCA in part of thereservation resource for the terminal apparatus 1-B (period forperforming the fourth CCA in FIG. 21 (fourth CAA period)) or/and part ofthe reservation resource for the terminal apparatus 1-C (period forperforming the fifth CCA in FIG. 21 (fifth CAA period)). Note that in acase that a reservation resource is reserved by the base stationapparatus (for example, a case that a reservation resource is reservedin advance through CCA by the base station apparatus), the terminalapparatus 1 can transmit the PRACH preamble without performing CCA. Thebase station apparatus may transmit, to the terminal apparatus,information indicating whether a reservation resource is reserved by thebase station apparatus. The information indicating whether thereservation resource is reserved by the base station apparatus may beincluded in the information notified through higher layer signalling orinformation included in the PDCCH (PDCCH order). The terminal apparatusmay determine whether to perform uplink LBT corresponding to PRACHpreamble transmission, based on the information indicating whether areservation resource is reserved by the base station apparatus.

Note that in a case that the terminal apparatus 1-C performs CCA in theperiod for performing the fourth CCA, it is preferable that the PRACHpreamble transmitted by the terminal apparatus 1-B by using thereservation resource 1-B be shorter than the period of the reservationresource 1-B and that the transmission of the PRACH preamble becompleted before the period for performing the fourth CCA.

In a case that e terminal apparatus 1-C performs PRACH preambletransmission in the reservation resource 1-C, the terminal apparatus 1-Ccan perform CCA in the period for performing the sixth CCA or theseventh CCA. The period for performing the sixth CCA is a periodconfigured immediately before the PRACH resource, and the terminal 1apparatus 1-C performs CCA in the period for performing the sixth CCA tothereby assume that the PRACH resource is reserved. The period forperforming the seventh CCA is in a first portion of the PRACH resource,and the terminal apparatus 1-C performs CCA in the period for performingthe seventh CCA to thereby assume that a resource for a later portionthan the period for performing the seventh CCA in the PRACH resource isreserved. Note that the period for performing the seventh CCA may beconfigured by including partial periods of the reservation resource 1-A,the reservation resource 1-B, the reservation resource 1-C, and thereservation resource 1-X. For example, the period for performing theseventh CCA may be configured as a period including part of thereservation resource 1-A from the time point of PRACH resource start.

Note that the period for performing the sixth CCA and the period forperforming the seventh CCA may be CCA periods configured in order forthe terminal apparatus 1-A or the terminal apparatus 1-B to transmit thePRACH preamble. Moreover, the period for performing the fourth CCA maybe configured as a partial period of the reservation resource for aterminal apparatus different from the terminal apparatus 1, configuredbefore the reservation resource configured in order for the terminalapparatus 1 to transmit the PRACH preamble. Moreover, the period forperforming the fifth CCA may be configured as a partial period of thereservation resource configured in order for the terminal apparatus 1 totransmit the PRACH preamble.

The terminal apparatus 1 may perform CCA in a period including part ofor all the period for performing the fourth CCA, the period forperforming the fifth CCA, the period for performing the sixth CCA, andthe period for performing the seventh CCA.

Note that the method of configuring reservation resources is not limitedto the example in FIG. 21, and the same reservation resource can beconfigured for multiple terminal apparatuses or a group of terminalapparatuses instead of a terminal apparatus.

The fourth CCA period may correspond to an ICCA period or may correspondto an ECCA period. The fifth CCA period may correspond to an ICCA periodor may correspond to an ECCA period.

In a case that the terminal apparatus 1-C performs CCA to transmit thePRACH preamble in the fourth CCA period, the period for the PRACHpreamble transmitted from the terminal apparatus 1-B is preferably inpart of the PRACH slot instead of the entire PRACH slot. In other words,a prescribed interval may be provided between the reservation resourcereserved by the terminal apparatus 1-B and the reservation resourcereserved by the terminal apparatus 1-C. Alternatively, a guard time maybe included in the PRACH preamble transmitted by the terminal apparatus1-B. The terminal apparatus 1-C may configure a period within the guardtime included in the PRACH preamble configured for the terminalapparatus 1-B, as the fourth CCA period. In consideration of error intime synchronization and the like of the terminal apparatus 1-B, aperiod offset with a prescribed period from the beginning of the guardtime included in the PRACH preamble configured for the terminalapparatus 1-B may be configured as the fourth CCA period. Note that theend of the fourth CCA period in this case may be configured earlier soas to match the beginning of the reservation resource configured for theterminal apparatus 1-C.

Details of uplink LBT will be described below.

“Before performing an uplink transmission” or “before transmitting theuplink” means before an indicated timing (subframe) for the uplinktransmission.

In the first uplink LBT, the CCA check is performed multiple times usingthe backoff counter before the indicated timing for the uplinktransmission. The terminal apparatus attempts the CCA check the numberof times equal to a value in the backoff counter. In a case that all theCCA checks result in the determination that the channel is idle, theterminal apparatus can acquire the right to access the channel totransmit the uplink.

FIG. 8 illustrates an example of a procedure of the first uplink LBT. Ina case of detecting the uplink grant (S802) in the idle state (S801),the terminal apparatus performs first CCA (S803). In the first CCA,first, the terminal apparatus randomly generates a counter value Nwithin the range from 0 to q−1 (S8031). Note that, in a case that anumerical value associated with the counter value N is indicated by thebase station apparatus using the uplink grant, the terminal apparatususes the counter value N based on the numerical value instead ofgenerating a counter value. Note that, in a case that the last LBT hasnot set the counter value to 0, with a value remaining in the counter,the terminal apparatus may use the remaining counter value N instead ofgenerating a counter value N. Then, the terminal apparatus starts CCA ata prescribed timing (S8032). The terminal apparatus senses the channel(medium) during one CCA slot duration (S8033) to determine whether thechannel is idle or busy (S8034). The terminal apparatus decrements thecounter value N by one (S8035) in a case of determining that the channelis idle, and returns to the idle state (S801) instead of performing theuplink transmission indicated by the uplink grant in a case ofdetermining that the channel is busy. The terminal apparatus thendetermines whether the counter value is 0 (S8036), and in a case thatthe counter value is 0, acquires the right to access the channel andproceeds to a transmission operation (S804, S805). On the other hand, ina case that the counter value is not 0, the terminal apparatus sensesthe channel (medium) during one CCA slot duration again (S8033). Notethat, in a case that the counter value N is generated, the value in thecollision window q is updated to a value from X to Y according to thechannel state (S8037). In a transmission process, the terminal apparatusdetermines whether to actually perform an uplink transmission at thattiming (S804), and in a case of determining to perform the uplinktransmission, performs the uplink transmission (S805). In a case ofdetermining not to perform the uplink transmission, the terminalapparatus returns to the idle state (S801) instead of performing theuplink transmission indicated by the uplink grant.

The period of the first CCA may be preferably the same as the ECCAperiod in the downlink LBT.

Note that the ICCA may be performed before the first CCA as is the casewith the downlink LBT. However, even in a case that the ICCA results inthe determination that the channel is idle, the uplink is nottransmitted and the procedure proceeds to the first CCA operation.

In the second uplink LBT, the CCA check is performed only once beforethe instructed timing for the uplink transmission. The terminalapparatus attempts the CCA check once. In a case of determining that thechannel is idle as a result of the CCA check, the terminal apparatus canacquire the right to access the channel to transmit the uplink.

FIG. 9 illustrates an example of a procedure of the second uplink LBT.In a case of detecting the uplink grant (S902) in the idle state (S901),the terminal apparatus performs second CCA (S903). In the second CCA,the terminal apparatus starts CCA at a prescribed timing (S9031). Theterminal apparatus performs the CCA check during a CCA period to sensewhether the channel is idle or busy (S9032). In a case of determiningthat the channel is idle as a result of the second CCA (S903), the basestation apparatus acquires the right to access the channel and proceedsto a transmission operation. On the other hand, in a case of determiningthat the channel is busy as a result of the second CCA (S903), theterminal apparatus returns to the idle state (S901) instead ofperforming the uplink transmission indicated by the uplink grant. Afterproceeding to the transmission operation, the terminal apparatusdetermines whether to actually perform an uplink transmission at thattiming (S904), and in a case of determining to perform the uplinktransmission, the terminal apparatus performs the uplink transmission(S905). In a case of determining not to perform the uplink transmission,the terminal apparatus returns to the idle state (S901) instead ofperforming the uplink transmission indicated by the uplink grant.

The period of the second CCA may be preferably the same as the ICCAperiod in the downlink LBT.

The terminal apparatus may switch the first PRACH preamble transmissionand the second PRACH preamble transmission, based on higher layersignalling. For example, the higher layer signalling is RRC signaling inthe RRC layer. The terminal apparatus may switch the first and thesecond PRACH preamble transmissions, based on the value of a prescribedfield included in the RRC signaling. The prescribed field refers to, forexample, 1-bit information specifying the configuration of the PRACHpreamble configuration for the terminal apparatus. In a case that theprescribed 1 bit is indicative of 0 (false, invalid, impossible, firststate), the terminal apparatus transmits the first or second PRACHpreamble. In a case that the prescribed 1 bit is indicative of 1 (true,valid, possible, second state), the terminal apparatus transmits thesecond or first PRACH preamble.

The terminal apparatus switches the first and second PRACH preambles,based on the configuration of the PRACH resource configured by higherlayers. For example, in a case that the configuration of the PRACHresource includes a PRACH slot, the terminal apparatus transmits thesecond PRACH preamble; in a case that the configuration of the PRACHresource does not include a PRACH slot, the terminal apparatus transmitsthe first PRACH preamble.

The terminal apparatus switches the first and second PRACH preambles,based on the information on signalling of the base station apparatus(e.g., PDCCH order). The terminal apparatus may switch the first and thesecond PRACH preamble transmissions, based on the value of a prescribedfield included in the PDCCH order. The prescribed field refers to, forexample, 1-bit information specifying the configuration of the PRACHpreamble for the terminal apparatus. In a case that the prescribed 1 bitis indicative of 0 (false, invalid, impossible, first state), theterminal apparatus may transmit the first or second PRACH preamble. In acase that the prescribed 1 bit is indicative of 1 (true, valid,possible, second state), the terminal apparatus may transmit the secondor first PRACH preamble. Specifically, in a case that the base stationapparatus indicates start of a random access process to a mobile stationapparatus, the base station apparatus may transmit downlink controlinformation on a specific format using prescribed code points (e.g., theflag indicating the format type is set at “1”, the flag indicating theradio resource allocation method is set at “0”, and the informationindicating radio resource allocation is all set at “1”) for particularregions, and a downlink control channel including a C-RNTI assigned tothe mobile station apparatus to which the start of the random accessprocess is indicated. The regions other than the particular regions inthe downlink control channel indicating the start of the random accessprocess includes information indicating a signature number andinformation indicating random access channel radio resources to whichthe mobile station apparatus may map a preamble in the random accesschannel radio resources to which downlink carrier elements correspond.

The terminal apparatus may transmit the first PRACH preamble in a casethat the PDCCH order is detected in the first secondary cell andtransmit the second PRACH preamble in a case that the PDCCH order isdetected in the secondary cell.

The terminal apparatus may switch the first and second PRACH preambles,based on the information on the PRACH resource notified by the basestation apparatus. For example, in a case that the information on thePRACH resource (PRACH Mask Index or the like) is notified throughsignalling by the base station apparatus (e.g., PRCCH order) andtransmission of the PRACH preamble in the PRACH slot is configured, theterminal apparatus may transmit the second PRACH preamble. In contrast,in a case that the information on the PRACH resource (PRACH Mask Indexor the like) is notified through signaling by the base station apparatus(e.g., PRCCH order) and transmission of the PRACH preamble in a PRACHresource that is not the PRACH slot is configured, the terminalapparatus may transmit the second PRACH preamble.

The terminal apparatus may switch the first and the second PRACHpreambles, based on the type of the serving cell including the PRACHresource. For example, in a case that the PRACH resource is included ina first serving cell, the terminal apparatus transmits the first PRACHpreamble; in a case that the PRACH resource is included a second servingcell, the terminal apparatus transmits the second PRACH preamble.

For example, the second PRACH is transmitted only in the LAA Scellor/and, the LAA Pscell (band 46, frame structure type 3) or/and thesecond secondary cell, while the first PRACH is transmitted only in thefirst secondary cell.

In a case that the terminal apparatus has transmitted, to the basestation apparatus, capability information indicating that the functionof transmitting the second PRACH preamble is provided, the terminalapparatus may transmit the second PRACH preamble. In a case that theterminal apparatus has transmitted, to the base station apparatus,capability information indicating that the function of transmitting thesecond PRACH preamble is not provided, the terminal apparatus maytransmit the first PRACH preamble. In a case that the terminal apparatusdoes not have the function of transmitting, to the base stationapparatus, capability information on the function of transmitting thesecond PRACH preamble, the terminal apparatus may transmit the firstPRACH preamble.

The terminal apparatus may transmit the first PRACH preamble in a casethat the information indicating the component carrier to which the PDCCHis allocated (Carrier Indicator Field (CIF) or the like) included in thedetected PDCCH order indicates the first secondary cell and may transmitthe second PRACH preamble in a case that the information indicates thesecond secondary cell.

Differences between the downlink LBT and the uplink LBT will be detailedbelow.

In the downlink LBT, the base station apparatus performs the CCA check.On the other hand, in the uplink LBT, the terminal apparatus performsthe CCA check.

In the downlink LBT, LBT processing is started in a case thatinformation (data, buffer, load, traffic) that needs to be transmittedhas occurred. On the other hand, for the uplink LBT, LBT processing isstarted in a case that an uplink transmission is indicated by the basestation apparatus.

Note that the ICCA period of the downlink LBT may be preferably the sameas the period of the second CCA. Note that the ECCA period of thedownlink LBT may be preferably the same as the period of the first ICCA.

Next, specific examples are provided regarding switching between a caseof transmitting the uplink following the first uplink LBT and a case oftransmitting the uplink following the second uplink LBT or transmittingthe uplink with no uplink LBT.

By way of example, the procedure of the uplink LBT is switched based ona prescribed field included in the uplink grant (DCI format 0 or 4)indicating an uplink transmission.

The prescribed field refers to, for example, 1-bit informationspecifying the uplink LBT for the terminal apparatus. In other words,the prescribed field refers to 1-bit information indicating whether thechannel has been successfully reserved (provided) in the subframeimmediately before the subframe indicated by the uplink grant. In a casethat a prescribed 1 bit is indicative of 0 (false, invalid, impossible,first state), the terminal apparatus performs the first uplink LBTbefore the uplink transmission. On the other hand, in a case that theprescribed 1 bit is indicative of 1 (true, valid, possible, secondstate), the terminal apparatus performs the second uplink LBT before theuplink transmission or performs no uplink LBT.

Alternatively, the prescribed field refers to, for example, informationassociated with the counter value N used in the first uplink LBT. In acase that the prescribed field is 0 (invalid, impossible), the terminalapparatus performs the second uplink LBT before the uplink transmissionor performs no uplink LBT. On the other hand, in a case that theprescribed field contains a numerical value other than 0 (invalid,impossible), the terminal apparatus generates a counter value N, basedon the numerical value to perform the first uplink LBT.

The information associated with the counter value N is, for example, thecounter value N. The terminal apparatus sets the value of the prescribedfield at the counter value N instead of generating a counter value N byitself.

Moreover, the information associated with the counter value N is, forexample, index information indicative of the configured counter value N.In a case that multiple candidates for the counter value N areconfigured for the terminal apparatus by dedicated RRC and that thevalue in the prescribed field has been acquired, the configured countervalue N corresponding to the information in the field is used.

Moreover, the information associated with the counter value N is, forexample, information associated with the collision window q. Multiplecandidates for the collision window q are configured for the terminalapparatus by the dedicated RRC. In a case of acquiring the value in theprescribed field, the terminal apparatus generates a counter value N byusing the configured value of the collision window q corresponding tothe information in the field. Note that the information associated withthe collision window q may be the value of the collision window q.

Note that the above-described examples may include switching between acase of transmitting the uplink following the second uplink LBT and acase of transmitting the uplink with no uplink LBT. Specifically, in acase that the prescribed 1 bit is indicative of 0 (false, invalid,impossible, first state), the terminal apparatus performs the seconduplink LBT before the uplink transmission. On the other hand, in a casethat the prescribed 1 bit is indicative of 1 (true, valid, possible,second state), the terminal apparatus performs no uplink LBT before theuplink transmission.

The information in the prescribed field may be information indicatingwhether to generate a gap where LBT is to be performed. For example, ina case that 1 bit in the prescribed field is 1, the terminal apparatustransmits the PUSCH with a gap of prescribed SC-FDMA symbols before thetransmission. In a case that the 1 bit in the prescribed field is 0, theterminal apparatus transmits the PUSCH with no gap of prescribed SC-FDMAsymbols before the transmission. The prescribed SC-FDMA symbols are, forexample, several SC-FDMA symbols at the beginning or end of the subframeor a slot at the beginning or the end of the subframe.

Note that the prescribed field may be used along with any other field.For example, the procedure of the uplink LBT may be switched inaccordance with an SRS request field. Specifically, the terminalapparatus performs the second uplink LBT before the uplink transmissionin a case that the SRS request field is indicative of 0, and performs nouplink LBT in a case that the SRS request field is indicative of 1. In acase that the SRS request field is indicative of 0, nothing istransmitted in the last one SC-FDMA symbol of the subframe. The terminalapparatus performs the second uplink LBT in the last one SC-FDMA symbol.

By way of example, the procedure of the uplink LBT is switched based ona prescribed field included in DCI different from an uplink grant.

The DCI different from the uplink grant refers to, for example, DCI fornotifying the terminal apparatus whether the downlink transmission(transmission burst) has been performed in a subframe indicated in theDCI. Specifically, the subframe indicated in the DCI includes a subframeimmediately before the uplink transmission, and a prescribed field inthe DCI is information corresponding to a notification as to whether thedownlink transmission is to be performed. In a case that the prescribedfield in the DCI indicates that the downlink transmission is not to beperformed, the terminal apparatus performs the first uplink LBT beforethe uplink transmission. On the other hand, in a case that theprescribed field in the DCI indicates that the downlink transmission isto be performed, the terminal apparatus performs the second uplink LBTbefore the uplink transmission or performs no uplink LBT.

The information notified in the DCI different from the uplink grant is,for example, the length of the downlink transmission. The information isindicative of the beginning and/or end of the downlink transmission.Predefinition or pre-configuration of the length of the downlinktransmission allows the terminal apparatus to recognize the length ofthe downlink transmission, based only on the information about thebeginning or end of the downlink transmission. As an example, in a casethat the length corresponds to one subframe and that the information inthe DCI indicates that the downlink transmission starts at the beginningof a prescribed subframe, the terminal apparatus recognizes that thedownlink transmission is to be performed in the one indicated subframe.

Moreover, the DCI different from the uplink grant may be preferablymapped in the non-LAA cell. Specifically, the DCI is mapped in thecommon search space present in the primary cell or the primary secondarycell, and one piece of DCI allows notification of informationcorresponding to multiple serving cells.

Furthermore, the DCI different from the uplink grant is scrambled withdedicated RNTI different from C-RNTI (RNTI for downlink transmissionnotification only, B-RNTI). The RNTI for downlink transmissionnotification only may be preferably configured individually for multipleterminal apparatuses but may be configured with a value common to theterminal apparatuses.

Moreover, the DCI different from the uplink grant, for example, has thesame format size as that of DCI format 1C used for very small-scalescheduling for one PDSCH codeword, notification of an MCCH change, orTDD reconfiguration. Alternatively, the DCI, for example, has the sameformat size as that of DCI format 3 or DCI format 3A used to transmit aTPC command for the PUCCH or the PUSCH.

Note that the DCI different from the uplink grant may correspond to anotification as to whether the uplink transmission (transmission burst)has been performed in a subframe indicated in the DCI.

Note that the above-described examples may include switching between acase of transmitting the uplink following the second uplink LBT and acase of transmitting the uplink with no uplink LBT. Specifically, in acase that the prescribed field in the DCI indicates that the downlinktransmission is not to be performed, the terminal apparatus performs thesecond uplink LBT before the uplink transmission. On the other hand, ina case that the prescribed field in the DCI indicates that the downlinktransmission is to be performed, the terminal apparatus performs nouplink LBT before the uplink transmission.

By way of example, the procedure of the uplink LBT is switched accordingto the type of uplink channel or signal scheduled to be transmitted.

For example, the terminal apparatus performs the first uplink LBT beforea transmission of the PUSCH. The terminal apparatus performs the seconduplink LBT before the PRACH or performs no uplink LBT.

For example, the terminal apparatus performs the first uplink LBT beforea transmission of the SRS with the PUSCH. The terminal apparatusperforms the second uplink LBT before the SRS without the PUSCH orperforms no uplink LBT.

By way of example, the procedure of the uplink LBT is switched dependingon whether a transmission of a downlink signal or channel from a cell towhich the terminal apparatus is connected has been detected before theterminal apparatus transmits the uplink.

For example, a comparison between the received power of the CRS and athreshold is used as a reference for detection of a transmission of adownlink signal or channel from the cell to which the terminal apparatusis connected. In a case that the terminal apparatus determines that thereceived power of an RE on which the CRS of antenna port 0 (or antennaport 1, 2, 3) is mapped is smaller than a prescribed threshold in thesubframe immediately before the subframe for the uplink transmission,the terminal apparatus performs the first uplink LBT before the uplinktransmission. On the other hand, in a case that the terminal apparatusdetermines that the received power of the RE on which the CRS of antennaport 0 (or antenna port 1, 2, 3) is mapped exceeds the prescribedthreshold in the subframe immediately before the subframe for the uplinktransmission, the terminal apparatus performs the second uplink LBTbefore the uplink transmission or performs no uplink LBT.

For example, whether the reservation signal has been successfullydetected is used as the reference for detection of a transmission of thedownlink signal or channel from the cell to which the terminal apparatusis connected. In a case that the length of the downlink transmission ispredefined or pre-configured and that the terminal apparatus hassuccessfully detected the reservation signal, whether the downlinktransmission is to be performed in the subframe immediately before thesubframe for the uplink transmission can be determined based on the timeof the detection of the reservation signal (subframe, symbol, RE, Ts)and the length of the reservation signal. In a case of determining thatthe downlink transmission is not to be performed in the subframeimmediately before the subframe for the uplink transmission, theterminal apparatus performs the first uplink LBT before the uplinktransmission. On the other hand, in a case of determining that thedownlink transmission is to be performed in the subframe immediatelybefore the subframe for the uplink transmission, the terminal apparatusperforms the second uplink LBT before the uplink transmission orperforms no uplink LBT. A reference as to whether the terminal apparatushas successfully detected the reservation signal is, for example, acomparison between the received power of the RE to which the reservationsignal is assigned and a prescribed threshold.

For example, whether the PDCCH or the EPDCCH has successfully beendetected is used as the reference for detection of a transmission of thedownlink signal or channel from the cell to which terminal apparatus isconnected. In a case that the PDCCH or the EPDCCH has successfully beendecoded in the subframe immediately before the subframe for the uplinktransmission, the terminal apparatus can recognize that the subframe isreserved by the terminal apparatus as a downlink subframe. In otherwords, in a case that the PDCCH or the EPDCCH has successfully beendecoded in the subframe immediately before the subframe for the uplinktransmission, the terminal apparatus performs the first uplink LBTbefore the uplink transmission. On the other hand, in a case that thedecoding of the PDCCH or the EPDCCH fails in the subframe immediatelybefore the subframe for the uplink transmission, the terminal apparatusperforms the second uplink LBT before the uplink transmission orperforms no uplink LBT.

For example, whether the PDSCH has successfully been detected is used asthe reference for detection of a transmission of the downlink signal orchannel from the cell to which the terminal apparatus is connected. In acase that the PDSCH has successfully been decoded in the subframeimmediately before the subframe for the uplink transmission, theterminal apparatus can recognize that the subframe is reserved by thebase station apparatus as a downlink subframe. In other words, in a casethat the PDSCH has successfully been decoded in the subframe immediatelybefore the subframe for the uplink transmission, the terminal apparatusperforms the first uplink LBT before the uplink transmission. On theother hand, in a case that the decoding of the PDSCH fails in thesubframe immediately before the subframe for the uplink transmission,the terminal apparatus performs the second uplink LBT before the uplinktransmission or performs no uplink LBT.

For example, whether the DMRS has successfully been detected is used asthe reference for detection of a transmission of the downlink signal orchannel from the cell to which the terminal apparatus is connected. In acase that the DMRS has successfully been detected in the subframeimmediately before the subframe for the uplink transmission, theterminal apparatus cart recognize that, the subframe is reserved by thebase station apparatus as a downlink subframe. In other words, in a casethat the DMRS has successfully been decoded in the subframe immediatelybefore the subframe for the uplink transmission, the terminal apparatusperforms the first uplink LBT before the uplink transmission. On theother hand, in a case that the DMRS has successfully been detected inthe subframe immediately before the subframe for the uplinktransmission, the terminal apparatus performs the second uplink LBTbefore the uplink transmission or performs no uplink LBT. The referenceas to whether the terminal apparatus has successfully detected thereservation signal is, for example, a comparison between the receivedpower of an RE to which the DMRS is assigned and a prescribed threshold.In other words, the reference is a comparison between the received powerof antenna port 7 or 9 and the prescribed threshold.

By way of example, the procedure of the uplink LBT is switched dependingon whether the terminal apparatus has transmitted any uplink signal orchannel before transmitting the uplink.

For example, in a case that the terminal apparatus has transmitted thePUSCH in the subframe immediately before the subframe for the uplinktransmission, the transmission can be performed without LBT in thissubframe because the channel has successfully been reserved for thesubframe as an uplink subframe. In other words, in a case that theterminal apparatus has not transmitted the PUSCH in the subframeimmediately before the subframe for the uplink transmission, theterminal apparatus performs the first uplink LBT or the second uplinkLBT before the uplink transmission. On the other hand, in a case thatthe terminal apparatus has transmitted the PUSCH in the subframeimmediately before the subframe for the uplink transmission, theterminal apparatus performs no uplink LBT.

For example, in a case that the terminal apparatus has transmitted theSRS in the subframe immediately before the subframe for the uplinktransmission, the transmission can be performed without LBT because thechannel has successfully been reserved for the subframe as an uplinksubframe. In other words, in a case that the terminal apparatus has nottransmitted the SRS in the subframe immediately before the subframe forthe uplink transmission, the terminal apparatus performs the firstuplink LBT or the second uplink LBT before the uplink transmission. Onthe other hand, in a case of having transmitted the SRS in the subframeimmediately before the subframe for the uplink transmission, theterminal apparatus performs no uplink LBT.

For example, in a case that the terminal apparatus has transmitted thePRACH in the subframe immediately before the subframe for the uplinktransmission, the transmission can be performed in this subframe withoutLBT because the channel has been successfully reserved for the subframeas an uplink subframe. In other words, in a case that the terminalapparatus has not transmitted the PRACH in the subframe immediatelybefore the subframe for the uplink transmission, the terminal apparatusperforms the first uplink LBT or the second uplink LBT before the uplinktransmission. On the other hand, in a case of having transmitted thePRACH in the subframe immediately before the subframe for the uplinktransmission, the terminal apparatus performs no uplink LBT.

By way of example, the procedure of the uplink LBT is switched accordingto the configuration provided by the higher layer.

The configuration provided by the higher layer refers to, for example,configuration information specifying the procedure of the uplink LBT. Ina case that a configuration specifying the first uplink LBT is providedfor the terminal apparatus, the terminal apparatus performs the firstuplink LBT before an uplink transmission in the LAA cell for theterminal apparatus. In a case that a configuration specifying the seconduplink LBT is provided for the terminal apparatus, the terminalapparatus performs the second uplink LBT before an uplink transmissionin the LAA cell for the terminal apparatus. In a case that aconfiguration specifying that no uplink LBT is performed for theterminal apparatus is provided, the terminal apparatus performs nouplink LBT before performing the uplink transmission in the LAA cell.

The configuration provided by the higher layer refers to, for example, aconfiguration for cross carrier scheduling for the LAA cell. In a casethat, the cross carrier scheduling is configured for the LAA cell, theterminal apparatus performs the first uplink LBT. In a case that selfscheduling is configured for the LAA cell (in other words, in a casethat the cross carrier scheduling is not configured for the LAA cell),the terminal apparatus performs the second uplink LBT or performs nouplink LBT. In other words, in a case that the PDCCH or the EPDCCH inthe uplink grant for scheduling of the uplink transmission for the LAAcell is configured to be monitored for a cell other than the LAA cell,the terminal apparatus performs the first uplink LBT before the uplinktransmission. On the other hand, in a case that the PDCCH or the EPDCCHin the uplink grant for scheduling of the uplink transmission for theLAA cell is not configured to be monitored for other than the LAA cell,the terminal apparatus performs the second uplink LBT before the uplinktransmission or performs no uplink LBT.

The cross carrier scheduling may be configured for each of the downlinkgrant and the uplink grant. In that case, the above-described examplesof switching are regarded as switching as to whether the uplink grant isconfigured as the cross carrier scheduling.

The configuration provided by the higher layer refers to, for example,configuration of information indicative of a nation(s) where the LAAcell is operated. In a case that the information is indicative of aparticular nation(s) (for example, Japan or the Europe), the terminalapparatus performs the first uplink LBT before the uplink transmissionfor the LAA cell. On the other hand, in a case that the information isindicative of a country other than the particular nation(s) (forexample, the U.S. or China), the terminal apparatus performs the seconduplink LBT before the uplink transmission for the LAA cell or performsno uplink LBT. The information indicative of the nation(s) where the LAAcell is operated is, for example, Public Land Mobile Network (PLMN). ThePLMN is an identifier indicative of a country and an operator. The PLMNis included in the SIB1 and notified to the terminal apparatus. Notethat the procedure of the uplink LBT may be switched according to theoperating band in addition to the information about the nation(s) wherethe LAA cell is operated. The information indicative of the operatingband can be identified in information about the center frequency of thecarrier (EARFCN value) configured by the higher layer.

The particular country is a country where LBT needs to be performed. Thecountry information and the capability of the terminal apparatus may beassociated with each other. In other words, the terminal apparatus maybe linked with the particular nation(s) in such a manner that thecapability required for the terminal apparatus is specified.

The configuration provided by the higher layer refers to, for example,configuration of the first uplink LBT. The procedure of the uplink LBTis switched depending on whether the first uplink LBT has beenconfigured for the terminal apparatus. Specifically, in a case that thefirst uplink LBT has been configured by the higher layer, the terminalapparatus performs the first uplink LBT before the uplink transmissionfor the LAA cell. On the other hand, in a case that the first uplink LBThas not been configured by the higher layer, the terminal apparatusperforms the second uplink LBT before the uplink transmission for theLAA cell or performs no uplink LBT. The configuration of the firstuplink LBT includes, for example, information about the range X and Yfor determination of the collision window q, a CCA slot length, a CCAthreshold, and the like.

Note that the procedure of the uplink LBT may be switched depending onwhether the second uplink LBT has been configured for the terminalapparatus. Specifically, in a case that the second uplink LBT has beenconfigured by the higher layer, the terminal apparatus performs thefirst uplink LBT before the uplink transmission for the LAA cell. On theother hand, in a case that the second uplink LBT has been configured bythe higher layer, the terminal apparatus performs the second uplink LBTbefore the uplink transmission for the LAA cell. The configuration ofthe second uplink LBT includes, for example, the value of the collisionwindow q, the CCA slot length, the CCA threshold, and the like.

The configuration of the first uplink LBT and the configuration of thesecond uplink LBT may be preferably specific to each cell. Note that onepiece of configuration information may be configured commonly for allthe cells configured as serving cells. This is not applicable to non-LAAcells configured as serving cells.

Note that the switching may be performed based on a combination ofmultiple configurations provided by the higher layer. In a specificexample, in a case that the cross carrier scheduling is not configuredfor the LAA cell and that notification that the nation(s) where the LAAcell is operated is the particular nation(s) has been provided, theterminal apparatus performs the second uplink LBT before the uplinktransmission for the LAA cell or performs no uplink LBT. In a case thatthe cross carrier scheduling is configured for the LAA cell and thatnotification that the nation(s) where the LAA cell is operated is otherthan the particular nation(s) has been provided, the terminal apparatusperforms the first uplink LBT before the uplink transmission for the LAAcell.

Moreover, the switching may be performed in a case of combining multipleones of the above-described examples. In a specific example, in a casethat the self scheduling is configured for the LAA cell and that aprescribed field included in the uplink grant indicating the uplinktransmission indicates that the first LBT is to be performed, theterminal apparatus performs the first uplink LBT before the uplinktransmission for the LAA cell. Otherwise the terminal apparatus performsthe second uplink LBT before the uplink transmission for the LAA cell orperforms no uplink LBT.

Note that the parameter may be switched depending on the above-describedexamples. In a specific example, in a case that the terminal apparatusperforms the first uplink LBT but the self scheduling is configured forthe LAA cell, a value configured by the higher layer (RRC) is applied tothe collision window q, and in a case that the cross carrier schedulingis configured for the LAA cell, the collision window q is updated ateach transmission opportunity, based on the value configured by thehigher layer (RRC).

Note that the above-described examples may include switching between acase of transmitting the uplink following the second uplink LBT and acase of transmitting the uplink with no uplink LBT. In other words, in acase that the PDCCH or the EPDCCH in the uplink grant for scheduling ofthe uplink transmission for the LAA cell is configured to be monitoredfor a cell other than the LAA cell, the terminal apparatus performs thesecond uplink LBT before the uplink transmission. On the other hand, ina case that the PDCCH or the EPDCCH in the uplink grant for schedulingof the uplink transmission for the LAA cell is not configured to bemonitored for a cell other than the LAA cell, the terminal apparatusperforms no uplink LBT before the uplink transmission.

FIG. 10 illustrates an example of frequency multiplexing of the PUSCH inthe LAA cell. In the LAA cell, PUSCH resources are not contiguouslyallocated but are allocated at intervals of several subcarriers in thefrequency direction. The PUSCH is allocated among different terminalapparatuses in an interlaced manner such that subcarriers are nested. InFIG. 10, the PUSCH is allocated at intervals of three subcarriers, andthe PUSCH for three terminal apparatuses is allocated in such a manneras to be interlaced for each subcarrier. This allows the terminalapparatuses to utilize the entire bandwidth with a few resources.

To allow frequency multiplexing or spatial multiplexing among multipleterminal apparatuses in the LAA cell by using the same subframes (timeresources), transmission timings for the terminal apparatuses need to beadjusted in such a manner that uplink channels and/or uplink signalsfrom the respective terminal apparatuses are simultaneously received bythe base station apparatus. Furthermore, in the LAA cell, the uplink LBTis performed before the uplink transmission. In a case that LBT isperformed based on the counter value N, the number of attempts toperform CCA and the time needed for LBT vary according to the countervalue N. The relationship between start timings for the uplinktransmission and the uplink LBT will be described below.

FIG. 11 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 11 is basedon operations in accordance with the procedure of the uplink LBT in FIG.8. The base station apparatus notifies each terminal apparatus of thetiming (subframe) for the uplink transmission. The timing for the uplinktransmission is implicitly notified, for example, based on a subframe inwhich the uplink grant is received. The terminal apparatus independentlygenerates a counter value N. The terminal apparatus estimates the timewhen the uplink LBT is completed from the counter value N and the CCAperiod to determine the LBT start timing. That is, the terminalapparatus can calculate the start timing for the uplink LBT, based onthe start timing for the uplink transmission and the number of the firstCCAs (counter value N). In other words, the CCA for the uplinktransmission starts (counter value N×CCA period) microseconds before thebeginning of the uplink subframe for the terminal apparatus.

The terminal apparatus having determined that the channel is busy as aresult of the CCA does not perform the uplink transmission at theindicated timing for the uplink transmission. At this time, the countervalue N is not discarded and is taken over by the next uplink LBT. Inother words, in a case that any counter value N remains in the counter,no counter value N is generated. Note that the counter value N may bediscarded and may not be taken over by the next uplink LBT depending onthe type of the DCI format or a particular parameter. For example, in acase of receiving information indicative of the first transmissionthrough a parameter indicative of new data (new data indicator), theterminal apparatus discards the counter value N and does not take overthe counter value N to the next uplink LBT. Moreover, the counter valueN may be linked with the HARQ process. In other words, the counter valueN for the uplink LBT for the PUSCH is independent among different HARQprocesses.

Note that the uplink transmission may be performed in the middle of theuplink subframe. At that time, the CCA for the uplink transmissionstarts (counter value N×CCA period) microseconds before the beginning ofthe uplink transmission that the terminal apparatus is indicated toperform.

Note that the initial CCA may be performed in the uplink LBT. In thatcase, the CCA for the uplink transmission starts (initial CCAperiod+counter value N+CCA period) microseconds before the beginning ofthe uplink subframe in which the terminal apparatus is indicated toperform the uplink transmission.

Note that, in a case that time is needed to switch from the receiver tothe transmitter, the start timing for the uplink LBT is determined withthe switching time taken into account. In other words, the CCA for theuplink transmission starts (counter value N×CCA period+time needed toswitch from the receiver to the transmitter) microseconds before thebeginning of the uplink subframe in which the terminal apparatus isindicated to perform the uplink transmission.

Note that the start timing of CCA for the uplink transmission may becalculated based on the downlink radio frame (downlink subframe). Inother words, the CCA for the uplink transmission starts (counter valueN×CCA period+uplink-downlink frame timing adjustment time) microsecondsbefore the beginning of the downlink subframe corresponding to theuplink subframe in which the terminal apparatus is indicated to performthe uplink transmission. Here, the uplink-downlink frame timingadjustment time is (N_(TA)+N_(TA_offset))×T_(s), N_(TA) is a terminalapparatus-specific parameter having a value from 0 to 20512 foradjustment of the uplink transmission timing, and N_(TA_offset) is aframe structure type-specific parameter for adjustment of the uplinktransmission timing.

Here, in the LAA cell, a value that can be taken by N_(TA) may belimited. In other words, in the LAA cell, the maximum value of N_(TA) issmaller than 20512.

FIG. 12 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 12 is basedon operations in accordance with the procedure of the uplink LBT in FIG.8. The base station apparatus notifies each terminal apparatus of thestart timing for the uplink LBT and information associated with thecounter value N. The start timing for the uplink LBT is implicitlynotified, for example, based on the subframe in which the uplink grantis received. The terminal apparatus can recognize the start timing forthe uplink transmission, based on the start timing for the uplink LBTand the counter value N. That is, the terminal apparatus can calculatethe start timing for the uplink transmission, based on the start timingfor the uplink LBT and the number of the first CCAs (counter value N).In other words, the uplink transmission starts (counter value N×CCAperiod) microseconds after the beginning of an uplink subframe in whichthe terminal apparatus is indicated to perform CCA. Here, the samecounter value N is configured for all the terminal apparatuses to bemultiplexed.

The information associated with the counter value N is, for example, thecounter value N. In a case of being notified of the counter value N, theterminal apparatus performs the uplink LBT by using the counter value N.

Moreover, the information associated with the counter value N is, forexample, a seed of random number used to generate the counter value N.The terminal apparatus generates the counter value N by using thenotified value and another parameter. Such another parameter is, forexample, an accumulated value of the HARQ-ACK for the PUSCH, the cellID, a subframe number, a system frame number, or the like.

The terminal apparatus having determined that the channel is busy as aresult of the CCA does not perform the uplink transmission at theindicated timing for the uplink transmission. At this time, the countervalue N is discarded and is not taken over to the next uplink LBT.

Note that the initial CCA may be performed in the uplink LBT. In thatcase, the uplink transmission starts (initial CCA period+counter valueN×CCA period) microseconds after the beginning of an uplink subframe inwhich the terminal apparatus is indicated to perform CCA.

Note that, in a case that time is needed to switch from the receiver tothe transmitter, the start timing for the uplink LBT is determined withthe switching time taken into account. In other words, the uplinktransmission starts (counter value N×CCA period+time needed to switchfrom the receiver to the transmitter) microseconds after the beginningof an uplink subframe in which the terminal apparatus is indicated toperform CCA.

Note that the uplink transmission may be calculated based on thedownlink radio frame (downlink subframe). In other words, the uplinktransmission starts (counter value N×CCA period−uplink-downlink frametiming adjustment time) microseconds after the beginning of the downlinksubframe corresponding to the uplink subframe in which the terminalapparatus is indicated to perform the CCA. Here, the uplink-downlinkframe timing adjustment time is (N_(TA)+N_(TA_offset))×T_(s), N_(TA) isa terminal apparatus-specific parameter having a value from 0 to 20512for adjustment of the uplink transmission timing, and N_(TA_) ^(offset)is a frame structure type-specific parameter for adjustment of theuplink transmission timing.

FIG. 13 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 13 is basedon operations in accordance with the procedure of the uplink LBT in FIG.9. The base station apparatus notifies each terminal apparatus of thetiming (subframe) for the uplink transmission. The timing for the uplinktransmission is implicitly notified, for example, based on a subframe inwhich the uplink grant is received. The terminal apparatus determinesthe time when the uplink LBT is completed based on the CCA period todetermine the LBT start timing. In other words, the CCA for the uplinktransmission starts (CCA period) microseconds before the beginning ofthe uplink subframe in which the terminal apparatus is indicated toperform the uplink transmission.

Note that, instead of the timing for the uplink transmission, the starttiming for the uplink LBT may be notified. In that case, the terminalapparatus can recognize the timing for the uplink transmission, based onthe CCA period. In other words, the CCA for the uplink transmissionstarts (CCA period) microseconds before the beginning of the uplinksubframe in which the terminal apparatus is indicated to perform theuplink transmission.

The terminal apparatus having determined that the channel is busy as aresult of the CCA does not perform the uplink transmission at theindicated timing for the uplink transmission.

FIG. 14 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 14 is basedon operations in accordance with the procedure of the uplink LBT in FIG.15 described below. The base station apparatus notifies each terminalapparatus of the timing (subframe) for the uplink transmission. Thetiming for the uplink transmission is implicitly notified, for example,based on a subframe in which the uplink grant is received. The terminalapparatus starts the first CCA at the start timing for the first CCA. Ina case that the counter value N becomes 0, the terminal apparatus waitsuntil a start timing for third CCA. Then, the terminal apparatusperforms the third CCA at the start, timing for the third CCA, and in acase that the channel is idle during the entire CCA period, performs theuplink transmission.

The start timing for the first CCA corresponds to, for example, thebeginning of the subframe before the uplink transmission. In otherwords, the first CCA for the uplink transmission starts at the beginningof the subframe closest to the beginning of the uplink transmission inwhich the terminal apparatus is indicated to perform.

Alternatively, the start timing for the first CCA is determined, forexample, based on the collision window q for the terminal apparatus. Inother words, the first CCA for the uplink transmission starts (collisionwindow q×CCA period) microseconds before the beginning of the uplinktransmission in which the terminal apparatus is indicated to perform.

The third CCA for the uplink transmission starts (third CCA period)microseconds before the beginning of the uplink subframe in which theterminal apparatus is indicated to perform the uplink transmission.

The third CCA period for the uplink transmission may be preferably thesame as the ICCA period.

FIG. 15 illustrates an example of the procedure of the uplink LBT. In acase of detecting the uplink grant (S1502) in the idle state (S1501),the terminal apparatus performs the first CCA (S1503). In the first CCA,first, the terminal apparatus randomly generates a counter value Nwithin the range from 0 to q−1 (S15031). Note that, in a case that anumerical value associated with the counter value N is indicated by thebase station apparatus using the uplink grant, the terminal apparatususes the counter value N based on the numerical value instead ofgenerating a counter value. Note that, in a case that the last LBT hasnot set the counter value to 0, with a value remaining in the counter,the terminal apparatus may use the remaining counter value N instead ofgenerating a counter value N. Then, the terminal apparatus starts CCA atthe prescribed tinting (S15032). The terminal apparatus senses thechannel (medium) during one CCA slot duration (S15033) to determinewhether the channel is idle or busy (S15034). The terminal apparatusdecrements the counter value N by one (S15035) in a case of determiningthat the channel is idle, and determines whether a third CCA checktiming has passed (S15038) in a case of determining that the channel isbusy. In a case that the third check timing has not passed, the terminalapparatus returns to the process of sensing the channel (medium) duringone CCA slot duration (S15033). In a case that the third CCA checktiming has passed, the terminal apparatus returns to the idle state(S1501) instead of performing the uplink transmission indicated by theuplink grant. After the counter value N is decremented by one, theterminal apparatus determines whether the counter value is 0 (S15036),and in a case that the counter value is 0, proceeds to the operation ofthe third CCA (S1504). On the other hand, in a case that the countervalue is not 0, the terminal apparatus senses the channel (medium)during one CCA slot duration again (S15033). Note that the value in thecollision window q obtained in a case that the counter value N isgenerated is updated to a value from X to Y according to the channelstate (S15037). Then, in the third CCA (S1504), the terminal apparatuswaits until a timing when the third CCA starts (S15041), and senses thechannel during the third CCA period (S15042). In a case of determiningthat the channel is busy as a result of the third CCA, the terminalapparatus returns to the idle state (S1501) instead of performing theuplink transmission indicated by the uplink grant. On the other hand, ina case of determining that the channel is idle as a result of the thirdCCA, the terminal apparatus acquires the right to access the channel andproceeds to a transmission operation (S1505, S1506). In a transmissionprocess, the terminal apparatus determines whether to actually performthe uplink transmission at that timing (S1505), and in a case ofdetermining that the uplink transmission is to be performed, performsthe uplink transmission (S1506). In a case of determining not to performthe uplink transmission, the terminal apparatus returns to the idlestate (S1501) instead of performing the uplink transmission indicated bythe uplink grant.

Note that the ICCA may be performed as is the case with the downlinkLBT. However, even in a case that the ICCA results in the determinationthat the channel is idle, the uplink is not transmitted and theprocedure proceeds to an ECCA operation.

The above-described constitution allows one subframe to be multiplexedto be transmitted and/or received in multiple terminal apparatuses, withlong-term CCA checks performed by random number backoff.

Note that the LAA cell may be preferably operated in accordance with ahalf duplex scheme. The terminal apparatus does not expect to receive,in a subframe in which an uplink transmission is being performed in oneLAA cell, a downlink signal and/or channel from another LAA cellconfigured as a serving cell. Specifically, the terminal apparatus doesnot expect to receive, in a subframe for which the PUSCH is scheduled inone LAA cell by DCI format 0/4, the PDCCH or the EPDCCH in all LAA cellsconfigured as serving cells. Furthermore, the terminal apparatusperforms, in the subframe, no uplink LBT in the LAA cell configured as aserving cell. Alternatively, the terminal apparatus may determine theresult of the uplink LBT of the LAA cell configured as a serving cell tobe busy in the subframe. Moreover, the terminal apparatus performs, in asubframe in which a downlink reception is being performed in one LAAcell, no uplink transmission in another LAA cell configured as a servingcell. In a specific example, the terminal apparatus performs no uplinktransmission in subframes configured as DMTC occasions. The terminalapparatus does not expect that the PUSCH is scheduled for subframesconfigured as DMTC occasions. Moreover, in a serving cell operated as anLAA cell, the terminal apparatus generates a guard period by avoidingreception of the end part of the downlink subframe immediately beforethe uplink subframe. Alternatively, in a serving cell operated as an LAAcell, the terminal apparatus generates a guard period by avoidingreception of the downlink subframe immediately before the uplinksubframe and reception of the downlink subframe immediately after theuplink subframe.

Note that the uplink LBT may be performed during the guard period.

Part of the content described in the present embodiment is rephrased asfollows.

The terminal apparatus includes a reception unit configured to receive aPDCCH, a transmission unit configured to transmit a PUSCH in a servingcell, and a CCA check unit configured to perform either first LBT forperforming a CCA check a number of times based on a random number beforea subframe for which a transmission of the PUSCH is indicated or secondLBT for performing a CCA check only once. The terminal apparatusswitches between the first LBT and the second LBT, based on a prescribedcondition.

Moreover, the information about the PDCCH is constituted by 1 bit. Thefirst LBT is performed before the subframe for which the transmission ofthe PUSCH is indicated in a case that the information about the PDCCH is1, and the second LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the informationabout the PDCCH is 0.

Moreover, the first LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that a downlinktransmission burst is not detected in a subframe immediately before asubframe in which the PUSCH is transmitted, and the second LBT isperformed before the subframe for which the transmission of the PUSCH isindicated in a case that the downlink transmission burst is detected inthe subframe immediately before the subframe in which the PUSCH istransmitted.

Moreover, the first LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the PDCCH isconfigured to be monitored in another serving cell different from theserving cell, and the second LBT is performed before the subframe forwhich the transmission of the PUSCH is indicated in a case that thePDCCH is not configured to be monitored in another serving celldifferent from the serving cell.

Moreover, the first LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the PUSCH is nottransmitted in the subframe immediately before the subframe in which thePUSCH is transmitted, and no LBT is performed before the subframe forwhich the transmission of the PUSCH is indicated in a case that thePUSCH is transmitted in the subframe immediately before the subframe inwhich the PUSCH is transmitted.

Furthermore, part of the content described in the present embodiment isrephrased as follows.

The terminal apparatus includes a transmission unit configured totransmit a PUSCH and a CCA check unit configured to perform LBT before asubframe for which a transmission of the PUSCH is indicated. Theterminal apparatus determines an LBT start time, based on a PUSCHtransmission start time and a CCA slot length.

Moreover, in the LBT, a CCA check is performed the prescribed number oftimes, and the LBT start time is determined based on the PUSCHtransmission start time and the CCA slot length.

Moreover, the terminal apparatus includes a reception unit configured toreceive a PDCCH. The number of the CCA checks is indicated by the PDCCH.

Note that the uplink LBT according to the present embodiment maysimilarly be applied to sidelink LBT for a sidelink transmission. Thesidelink transmission is used for device to device communication (D2D)between the terminal apparatuses.

Note that, in a case that one or more configurations (LAA-Config) whichare necessary for LAA communication for prescribed serving cell areconfigured to the terminal apparatus 1, the prescribed serving cell maybe regarded as the LAA cell. The configurations which are necessary forthe LAA communication are, for example, a parameter associated with areservation signal, a parameter associated with RSSI measurement, and aparameter associated with the second DS configuration.

In this regard, in a case that information (EARFCN value) on a centerfrequency associated with an LAA band for prescribed serving cell isconfigured to the terminal apparatus 1, the cell of the frequency may beregarded as the LAA cell. The LAA bands (LAA operating band) refer to,for example, bands meeting one or more features of bands whose bandnumbers are 252 to 255, bands which are neither a TDD band nor an FDDband, bands which are defined by a 5 GHz band, and bands which aredefined only by a 20 MHz bandwidth.

Note that the prescribed frequency may be preferably a frequency used bythe LAA cell. The prescribed frequency may be preferably a frequency ofcells which transmit the DSs, based on LBT. The prescribed frequency maybe preferably a frequency of cells operated in an unlicensed band. Theprescribed frequency may be preferably a frequency of an operating bandassociated with a prescribed index of the operating band. The prescribedfrequency may be preferably a frequency of an operating band associatedwith an index of the operating band for LAA. The prescribed frequencymay be preferably an operating band associated with a prescribed indexof the operating band (E-UTRA operating band). For example, theoperating bands may be preferably managed by a table. An associatedindex is given to each operating band managed by the table. The index islinked to n associated uplink operating band, downlink operating band,and a duplex mode. Note that the uplink operating band is an operatingband used for reception at the base station apparatus and transmissionat the terminal apparatus. The downlink operating band is an operatingband used for transmission at the base station apparatus and receptionat the terminal apparatus. Each of the uplink operating band and thedownlink operating band may be preferably given by a lower limitfrequency and an upper limit frequency (associated frequency band). Theduplex mode may be preferably given by TDD or FDD. The duplex mode inthe LAA cell may be other than TDD and FDD. For example, the duplex modein the FAA cell may be a transmission burst to be described below(optionally including at least a downlink burst or an uplink burst).

In a case that, for example, the operating bands are managed by thetable, operating bands associated with an index “1” to an index “44” maybe preferably licensed bands (bands which are not LAA), and operatingbands associated with an index “252 to an index “255” may be preferablyunlicensed bands (LAA bands). Note that the uplink operating band ispreferably not applied to the index “252” (n/a, not applicable). The5150 MHz to 5250 Hz is preferably applied to the downlink operatingband. FDD is preferably applied to the duplex mode. Furthermore, for theindex “253”, the uplink operating band may be preferably reserved(reserved to be used in future), and the downlink operating band may bepreferably reserved. FDD may be preferably applied to the duplex mode.Furthermore, for the index “254”, the uplink operating band may bepreferably reserved (reserved to be used in future), and the downlinkoperating band may be preferably reserved. FDD may be preferably appliedto the duplex mode. Note that the uplink operating band may not bepreferably applied to the index “255” (n/a, not applicable). The 5725MHz to 5850 Hz may be preferably applied to the downlink operating band.FDD may be preferably applied to the duplex mode.

Note that 5150 MHz to 5250 Hz and 5725 MHz to 5850 Hz are preferablyunlicensed bands (LAA bands). In other words, the prescribed frequenciesdescribed above may be preferably operating bands associated with theindex “252” to the index “255”.

Moreover, although the description has been given in each of theabove-described embodiment by using the terms “primary cell” and “PScell”, these terms may not be necessarily used. For example, “primarycell” in each of the above-described embodiments may be referred to as“master cell”, and “PS cell” in each of the above-described embodimentmay be referred to as “primary cell”.

Hereinafter, various aspects of the terminal apparatus 1 and the basestation apparatus 2 in the present embodiment will be described.

(1) A first aspect of the present embodiment is the terminal apparatus 1including: a reception unit configured to receive a first parameter anda second parameter through higher layer signalling; and a transmissionunit configured to transmit a random access preamble based on the firstparameter and a random access preamble based on the second parameter.The first parameter is used to configure a subframe number of a firstuplink subframe in which transmission of the random access preamblebased on the first parameter is allowed. The second parameter is used toconfigure a subframe number of a second uplink subframe in whichtransmission of the random access preamble based on the second parameteris allowed and a symbol number of an uplink symbol in the second uplinksubframe.

(2) In the first aspect of the present embodiment, the bandwidth for thetransmission of the random access preamble based on the second parameteris wider than the bandwidth for the transmission of the random accesspreamble based on the first parameter.

(3) In the first aspect of the present embodiment, the reception unitreceives the higher layer signalling including an information bit, andthe transmission of the random access preamble based on the firstparameter and the transmission of the random access preamble based onthe second parameter are controlled based on the state of theinformation bit.

(4) A second aspect of the present embodiment is the base stationapparatus 2 including: a transmission unit configured to transmit afirst parameter and a second parameter through higher layer signalling;and a reception unit configured to receive a random access preamblebased on the first parameter and a random access preamble based on thesecond parameter. The first parameter is used to configure a subframenumber of a first uplink subframe in which transmission of the randomaccess preamble based on the first parameter is allowed. The secondparameter is used to configure a subframe number of a second uplinksubframe in which transmission of the random access preamble based onthe second parameter is allowed and a symbol number of an uplink symbolin the second uplink subframe.

(5) In the second aspect of the present embodiment, the bandwidth forthe reception of the random access preamble based on the secondparameter is wider than the bandwidth for the reception of the randomaccess preamble based on the first parameter.

(6) In the second aspect of the present embodiment, the transmissionunit transmits the higher layer signalling including an information bit,and the reception of the random access preamble based on the firstparameter and the reception of the random access preamble based on thesecond parameter are controlled based on the state of the informationbit.

(7) A third aspect of the present embodiment is a communication methodof the terminal apparatus 1, the communication method including thesteps of: receiving a first parameter and a second parameter throughhigher layer signalling; and transmitting a random access preamble basedon the first parameter and a random access preamble based on the secondparameter. The first parameter is used to configure a subframe number ofa first uplink subframe in which transmission of the random accesspreamble based on the first parameter is allowed. The second parameteris used to configure a subframe number of a second uplink subframe inwhich transmission of the random access preamble based on the secondparameter is allowed and a symbol number of an uplink symbol in thesecond uplink subframe.

(8) A fourth aspect of the present embodiment is a communication methodof the base station apparatus 2, the communication method including thesteps of: transmitting a first parameter and a second parameter throughhigher layer signalling; and receiving a random access preamble based onthe first parameter and a random access preamble based on the secondparameter. The first parameter is used to configure a subframe number ofa first uplink subframe in which transmission of the random accesspreamble based on the first parameter is allowed. The second parameteris used to configure a subframe number of a second uplink subframe inwhich transmission of the random access preamble based on the secondparameter is allowed and a symbol number of an uplink symbol in thesecond uplink subframe.

(9) A fifth aspect of the present embodiment is the terminal apparatus 1including: a reception unit configured to receive downlink controlinformation on a PDCCH; and a transmission unit configured to transmit arandom access preamble. For a first frame structure type, the downlinkcontrol information is used to configure a subframe number of a firstuplink subframe in which transmission of the random access preamble isallowed. For a second frame structure type (the second frame structuretype may be applied to an LAA secondary cell operation cell), thedownlink control information is used to configure a subframe number of asecond uplink subframe in which transmission of the random accesspreamble is allowed and a symbol number of an uplink symbol in thesecond uplink subframe.

(10) In the fifth aspect of the present embodiment, the first framestructure type is applied to a frequency division duplex cell, and thesecond frame structure type (the second frame structure type may beapplied to an LAA secondary cell operation cell) is applied to alicensed assisted access cell.

(11) In the fifth aspect of the present embodiment, the reception unitreceives downlink control information to which CRC parity bits scrambledwith a RA-RNTI is attached, to be used for scheduling of a PDSCH onwhich a random access response is transmitted, the RA-RNTI is definedfor the first frame structure type in accordance with a firstcalculation expression based on the subframe number of the first uplinksubframe, and the RA-RNTI is defined for the second frame structure typein accordance with a second calculation expression based on the symbolnumber of the uplink symbol.

(12) A sixth aspect of the present embodiment is the base stationapparatus 2 including: a transmission unit configured to transmitdownlink control information on a PDCCH; and a reception unit configuredto receive a random access preamble. For a first frame structure type,the downlink control information is used to configure a subframe numberof a first uplink subframe in which transmission of the random accesspreamble is allowed. For a second frame structure type (the second framestructure type may be applied to an LAA secondary cell operation cell),the downlink control information is used to configure a subframe numberof a second uplink subframe in which transmission of the random accesspreamble is allowed and a symbol number of an uplink symbol in thesecond uplink subframe.

(13) In the sixth aspect of the present embodiment, the first framestructure type is applied to a frequency division duplex cell, and thesecond frame structure type (the second frame structure type may beapplied to an LAA secondary cell operation cell) is applied to alicensed assisted access cell.

(14) In the sixth aspect of the present embodiment, the transmissionunit transmits downlink control information to which CRC parity bitsscrambled with a RA-RNTI is attached, to be used for scheduling of aPDSCH on which a random access response is transmitted, the RA-RNTI isdefined for the first frame structure type in accordance with a firstcalculation expression based on the subframe number of the first uplinksubframe, and the RA-RNTI is defined for the second frame structure typein accordance with a second calculation expression based on the symbolnumber of the uplink symbol.

(15) A seventh aspect of the present embodiment is a communicationmethod of the terminal apparatus 1, the communication method includingthe steps of: receiving downlink control information on a PDCCH; andtransmitting a random access preamble. For a first frame structure type,the downlink control information is used to configure a subframe numberof a first uplink subframe in which transmission of the random accesspreamble is allowed. For a second frame structure type, the downlinkcontrol information is used to configure a subframe number of a seconduplink subframe in which transmission of the random access preamble isallowed and a symbol number of an uplink symbol in the second uplinksubframe.

(16) An eighth aspect of the present embodiment is a communicationmethod of the base station apparatus 2, the communication methodincluding the steps of: transmitting downlink control information on aPDCCH; and receiving a random access preamble. For a first framestructure type, the downlink control information is used to configure asubframe number of a first uplink subframe in which transmission of therandom access preamble is allowed. For a second frame structure type,the downlink control information is used to configure a subframe numberof a second uplink subframe in which transmission of the random accesspreamble is allowed and a symbol number of an uplink symbol in thesecond uplink subframe.

A program running on each of the base station apparatus 2 and theterminal apparatus 1 according to the present invention may be a program(a program for causing a computer to operate) that controls a CentralProcessing Unit (CPU) and the like in such a manner as to realize thefunctions according to the above-described embodiments of the presentinvention. The information handled in these apparatuses is temporarilystored in a Random Access Memory (RAM) while being processed.Thereafter, the information is stored in various types of Read OnlyMemory (ROM) such as a flash ROM and a Hard Disk Drive (HDD), and whennecessary, is read by the CPU to be modified or rewritten.

Moreover, the terminal apparatus 1 and the base station apparatus 2-1 orthe base station apparatus 2-2 according to the above-describedembodiments may be partially realized by the computer. In this case,this configuration may be realized by recording a program for realizingsuch con functions on a computer-readable recording medium causing acomputer system to read the program recorded on the recording medium forexecution.

Moreover, the “computer system” here is defined as a computer systembuilt into the terminal apparatus 1 or the base station apparatus 2-1 orthe base station apparatus 2-2, and the computer system includes an OSand hardware components such as peripheral devices. Furthermore, the“computer-readable recording medium” refers to a portable medium such asa flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and astorage device such as a hard disk built into the computer system.

Moreover, the “computer-readable recording medium” may include a mediumthat dynamically retains the program for a short period of time, such asa communication line that is used to transmit the program over a networksuch as the Internet or over a communication line such as a telephoneline, and a medium that retains, in that case, the program for a fixedperiod of time, such as a volatile memory within the computer systemwhich functions as a server or a client. Furthermore, the program may beconfigured to realize some of the functions described above, and alsomay be configured to be capable of realizing the functions describedabove in combination with a program already recorded in the computersystem.

Furthermore, the base station apparatus 2-1 or base station apparatus2-2 according to the above-described embodiments can be realized as anaggregation (an apparatus group) constituted of multiple apparatuses.Apparatuses constituting the apparatus group may be each equipped withsome or all portions of each function or each functional block of thebase station apparatus 2-1 or base station apparatus 2-2 according tothe above-described embodiments. It is only required that the apparatusgroup itself include general functions or general functional blocks ofthe base station apparatus 2-1 or base station apparatus 2-2.Furthermore, the terminal apparatus 1 according to the above-describedembodiments can also communicate with the base station apparatus as theaggregation.

Furthermore, the base station apparatus 2-1 or base station apparatus2-2 according to the above-described embodiments may be an EvolvedUniversal Terrestrial Radio Access Network (EUTRAN). Furthermore, thebase station apparatus 2-1 or base station apparatus 2-2 according tothe above-described embodiments may have some or all portions of afunction of a higher node for an eNodeB.

Furthermore, some or all portions of each of the terminal apparatus 1and the base station apparatus 2-1 or base station apparatus 2-2according to the above-described embodiments may be typically achievedas a Large-Scale Integration (LSI) that is an integrated circuit or maybe realized as a chip set. The functional blocks of each of the terminalapparatus 1 and the base station apparatus 2-1 or base station apparatus2-2 may be individually realized as a chip, or some or all of thefunctional blocks may be integrated into a chip. Furthermore, a circuitintegration technique is not limited to the LSI, and may be realizedwith a dedicated circuit or a general-purpose processor. Furthermore, ina case where with advances in semiconductor technology, a circuitintegration technology with which an LSI is replaced appears, it is alsopossible to use an integrated circuit based on the technology.

Furthermore, according to the above-described embodiments, the cellularmobile station apparatus is described as one example of a terminalapparatus or a communication apparatus, but the present invention is notlimited to this, and can be applied to a fixed-type electronic apparatusinstalled indoors or outdoors, or a stationary-type electronicapparatus, for example, a terminal apparatus or a communicationapparatus, such as an Audio-Video (AV) apparatus, a kitchen apparatus, acleaning or washing machine, an air-conditioning apparatus, officeequipment, a vending machine, and other household apparatuses.

The embodiments of the present invention have been described in detailabove referring to the drawings, but the specific configuration is notlimited to the embodiments and includes, for example, an amendment to adesign that falls within the scope that does not depart from the gist ofthe present invention. Furthermore, various modifications are possiblewithin the scope of the present invention defined by claims, andembodiments that are made by suitably combining technical meansdisclosed according to the different embodiments are also included inthe technical scope of the present invention. Furthermore, aconfiguration in which a constituent element that achieves the sameeffect is substituted for the one that is described according to theembodiments is also included in the technical scope of the presentinvention.

REFERENCE SIGNS LIST

-   301 Higher layer-   302 Control unit-   303 Codeword generation unit-   304 Downlink subframe generation unit-   305 Downlink reference signal generation unit-   306 OFDM signal transmission unit-   307 Transmit antenna-   308 Receive antenna-   309 SC-FDMA signal reception unit-   310 Uplink subframe processing unit-   311 Uplink control information extraction unit-   401 Receive antenna-   402 OFDM signal reception unit-   403 Downlink subframe processing unit-   404 Downlink reference signal extraction unit-   405 Transport block extraction unit-   406 Control unit-   407 Higher layer-   408 Channel state measurement unit-   409 Uplink subframe generation unit-   410 Uplink control information generation unit-   411 SC-FDMA signal transmission unit-   412 Transmit antenna-   1 (1-A, 1-B, 1-C) Terminal apparatus-   2 (2-1, 2-2) Base station apparatus

The invention claimed is:
 1. A terminal apparatus comprising:transmission circuitry configured to and/or programmed to transmit arandom access preamble on a PRACH (Physical Random Access Channel), andreception circuitry configured to and/or programmed to receive downlinkcontrol information with CRC (Cyclic Redundancy Check) parity bitsscrambled by a RA-RNTI (Random Access-Radio Network TemporaryIdentifier), wherein the RA-RNTI is determined at least based on an OFDM(Orthogonal Frequency-Division Multiplexing) symbol number at which thePRACH starts, and the PRACH is configured, from a plurality of PRACHseach of which starts at a different OFDM symbol number in a time domainwithin a duration, based on a PRACH mask index included in a PDCCHorder, the duration comprising 14 OFDM symbols.
 2. The terminalapparatus according to claim 1, wherein the RA-RNTI is determined atleast based on an index in addition to the OFDM symbol number, the indexis a duration number of the duration, 10 durations are included in aframe with 10 ms for the PRACH.
 3. The terminal apparatus according toclaim 2, wherein the duration is 1 ms.
 4. A base station apparatuscomprising: reception circuitry configured to and/or programmed toreceive a random access preamble on a PRACH (Physical Random AccessChannel), and transmission circuitry configured to and/or programmed totransmit downlink control information with CRC (Cyclic Redundancy Check)parity bits scrambled by a RA-RNTI (Random Access-Radio NetworkTemporary Identifier), wherein the RA-RNTI is determined at least basedon an OFDM (Orthogonal Frequency-Division Multiplexing) symbol number atwhich the PRACH starts, and the PRACH is configured, from a plurality ofPRACHs each of which starts at a different OFDM symbol number in a timedomain within a duration, based on a PRACH mask index included in aPDCCH order, the duration comprising 14 OFDM symbols.
 5. The basestation apparatus according to claim 4, wherein the RA-RNTI isdetermined at least based on an index in addition to the OFDM symbolnumber, the index is a duration number of the duration, 10 durations areincluded in a frame with 10 ms for the PRACH.
 6. The base stationapparatus according to claim 5, wherein the duration is 1 ms.
 7. Acommunication method of a terminal apparatus, the communication methodcomprising the steps of: transmitting a random access preamble on aPRACH (Physical Random Access Channel); and receiving downlink controlinformation with CRC (Cyclic Redundancy Check) parity bits scrambled bya RA-RNTI (Random Access-Radio Network Temporary Identifier), whereinthe RA-RNTI is determined at least based on an OFDM (OrthogonalFrequency-Division Multiplexing) symbol number at which the PRACHstarts, and the PRACH is configured, from a plurality of PRACHs each ofwhich starts at a different OFDM symbol number in a time domain within aduration, based on a PRACH mask index included in a PDCCH order, theduration comprising 14 OFDM symbols.
 8. A communication method of a basestation apparatus, the communication method comprising the steps of:receiving a random access preamble on a PRACH (Physical Random AccessChannel); and transmitting downlink control information with CRC (CyclicRedundancy Check) parity bits scrambled by a RA-RNTI (RandomAccess-Radio Network Temporary Identifier), wherein the RA-RNTI isdetermined at least based on an OFDM (Orthogonal Frequency-DivisionMultiplexing) symbol number at which the PRACH starts, and the PRACH isconfigured, from a plurality of PRACHs each of which starts at adifferent OFDM symbol number in a time domain within a duration, basedon a PRACH mask index included in a PDCCH order, the duration comprising14 OFDM symbols.